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ChromaTalk Archives: August 2011

Setup Guide for Behringer BCR2000 + Chroma

David Clarke [21030085++] · Mon, 01 Aug 2011 08:00:04 -0400

Following up to a ChromaTalk Mailing List discussion from June (Community work on Behringer BCR2000 'standard' setup for site?), several users wanted to try the Behringer BCR2000 with their Chroma/Expander, but they quickly ran into difficulties when attempting to get up and running.

Most of the noted problems were solved with answers from the list - but it seemed that first time users would benefit from having a setup guide.

To that end, one was created and is made available on the site this month: BCR2000 Set Up.

I not expecting this guide to be perfect - but it will hopefully be a starting point for new users. It is also hoped that new users will provide feedback on their experience and to make suggestions as to how the setup guide can be improved for future.

Thanks to Luca Sasdelli [21010226] for sharing initial BCR2000 setup information, Mike Grossman [21030350] for his feedback on parameter assignments and Chris Ryan [21030691] for his interactive feedback, editing and tailoring of materials for the site.

To accommodate the Setup Guide, Chris has reorganized the Behringer materials on the site. You’ll now find a general BCR2000 page with a sub-page for the Setup Guide, and one for the Chromatrol writeup previously provided by Matt Thomas [21010021].

pressure sensor > board unglued

Go to first message in thread, firmware update 215, pressure sensor board unglued, July 2011. See Pressure Sensor Retrofit Kit for reference.

Brian McCully [21030361] · Mon, 1 Aug 2011 10:28:48 -0700

No need to do any filing. Just lift up a bit while Opening or Closing the front panel. The hinge there is slotted and allows for such movement. Plenty of room otherwise. You can re-glue the sensor PCB to the wood spacer with any non-conductive adhesive. I used 3M 77 Spray Adhesive but Gorilla Glue or similar adhesive would work fine. Gently clamp while drying.

Hi Chris - yes, I'm pretty familiar with the lifting and separating of the front panel for clearance sake. Problem is that without filing out ~ 1/2" chink of the front panel, the vertical (mux?) board as is will not fit. The connector on front is in the way of the front panel's inner and upper lip. If the mux board was on the backside of the crossbar, and the cable connection was a few inches longer, than there would probably be no discussion about this. Like when I originally mounted it in backwards, it made a lot more sense because there's no room up front. If this was a manufacturing situ, I bet the mfg. engrs. would have balked at the design. But that doesn't at all negate your contribution. (I'm loathe to take my Chroma apart again and again, unlike other folks who enjoy re-building lawnmowers and old VW's. I'd rather just play music, instead.)

Interesting about removing the felt pads. There can be a fine line between sensor array position and completly inhibiting keyboard switching. So those two keys worked prior to the pressure sensor installation? Which keys? Sensor operation comes into play just after felt contact whether that be key pads or the sensor array felt proper. So you think the sensor felt negates the need for the key felt?

We have corresponded about this. An upper F# and C. To troubleshoot you had me take a popsicle stick and stick it between the key(s) and sensor(s) to see that they did work, at all. And so with the felts under the front, there wasn't adequate 'throw'. So I decided to remove all of the felts for uniformity sake. Those two keys are still more difficult to fully enable pressure, but overall, the action seems similar to when there was no pressure sensor installed. The keys are all uniformly spaced on my Chroma, so I don't think that the weights are hitting off-center. It's very hard to quantify how much different those two keys are, relative to the others. They just take a lot more push than the adjacent keys, for whatever reason. As to your question of whatever works the best - felt wise? Short of an R&D and marketing department, and about 10 or 20 Chromas for test beds, the mod is such a one-off that I'm personally ok with it, as is. As long as the Gorilla glue holds and all the sensors keep firing.

Chris Borman [21030194+] · Mon, 1 Aug 2011 14:55:46 -0400

That's right, I remember the issue you had with those keys. The reason for front mount was it looked like a good place to mount it and you have access to the sensitivity adjustment. The closed front panel on my Chroma does not hit the mux board at all and the cable length was selected for that position, so it seems there must be some dimensional assembly variation from Chroma to Chroma. The FSRs are mechanically fairly uniform across the entire array so maybe those two key actions are still not fully actuating the FSR. You could check the sensor using your finger to actuate and compare the F#/C with another sensor. That would determine if it's the sensor or still in the key action. The only other reason could be some variation in the FSR deposit on the mylar or some PCB trace or soldermask irregularity. I'll certainly swap out your sensor with a new one if that's the case.

For re-mounting, Look at the Sensor Array PCB drawing on the website, you will see holes spaced about each left and right sensor array, in between the sensor circuits. You need access to the PCB side under the wood spacer so this operation can only be done in the case of full separation. You can open up the holes slightly with a drill bit to allow a 2-56 screw. On a firm wood surface, gently drill right down through the PCB, FSR Mylar and felt. Mark the hole position on the felt with a dot from a Sharpie Marker, otherwise you might loose the hole in the felt. After you re-glue the PCB to the wood spacer, use 2-56 x 1/2" flat head wood screws to mechanically secure the entire assembly to the damper bar. Don't over tighten, just enough to secure it, screw head flush w/ the felt.

As far as the R&D dept, that is what the ChromaTalk family is for! A lot of Chroma issues have been resolved right here including a few with the CPS kit.

Brian McCully [21030361] · Wed, 3 Aug 2011 13:33:35 -0700

Chris et al, Re:

For re-mounting, Look at the Sensor Array PCB drawing on the website, you will see holes spaced about each left and right sensor array, in between the ... etc etc.

I expect the glue job to hold sans screws. Taking the whole cross-piece assembly out and unplugging everything would take a lot of time, and I'm prone to bending and breaking plugs (of course I bent a leg on the EPROM, installing the 215 firmware upgrade, but luckily was able to get it right the second time around...) Instead I followed your first suggestion, went out and bought (6) 2" C clamps, cut some brass and steel strips that I had from another project to underlay the (felted) pressure sensor strip to make sure that pressure was evenly and firmly applied (but not over-pressured) then gorilla glued it and clamped it back in place. Made sure the excess gorilla glue didn't spill out onto anything and now I'm waiting overnight before I unclamp it, put the keys back in place that I removed to allow for the C clamp spacing on the cross bar, and then close it up. I did notice that the FSR's do not exactly align with the key spacing. Overall, the keys are evenly spaced, and the FSR's are evenly spaced, but the outer border FSR's are about 1/16" or so less than the keys, so that centering the sensor strip means that the outer keys weights will not exactly fall on the FSR's. Not entirely sure if any key weights would trigger adjacent FSR's but there is some miniscule overlay. Not sure why the tolerances vary, but maybe my Chroma was constructed at a different place than yours (?) - hence the difference in the front panel clearance requirement as well.

Brian McCully [21030361] · Thu, 4 Aug 2011 09:55:26 -0700

pressure sensor > board unglued - now 4 dead FSR's

Waited for the overnight re-gluing to dry, removed all the clamps, and put it back together. Called up a patch with poly AT and discovered I now have 4 non-functioning polyAT FSR's. They are two adjacent keys, in two pairs. The G & Ab below the 32/33 panel switches, and the B & C below 43/44 switches. Tried putting a popsicle stick inbetween the weight and FSR and still there was no response from these 4 FSR's, at all. Also tried some other prodding and connector re-seating. All of the other key's FSR's work fine. Is there some common circuit or cabling that would affect these particular keys? Probably the gorilla glue expanded and separated some contacts. Think I'm going to need a new 'assembly', Chris...because I'm pretty sure I can't undo any of the Gorilla-ing at this point. :<(

Expander problems

Eric W. Mattei [21030443+] · Wed, 03 Aug 2011 11:41:58 -0700

Hello all

A friend of mine is looking to buy an Expander. If he doesn't buy it, I might. When you turn it on, the tapper taps repeatedly all by itself and won't stop. Also, all the LEDs blink repeatedly and won't stop. Has anybody ever heard of this symptom? What might cause it? Thanks!

Leonardo Ascarrunz [no serial number] · Wed, 3 Aug 2011 13:15:03 -0600

Could be many things. A good place to start is to replace the power supply.

David Clarke [21030085++] · Wed, 03 Aug 2011 16:13:19 -0400

... When you turn it on, the tapper taps repeatedly all by itself and won't stop. Also, all the LEDs blink repeatedly and won't stop. Has anybody ever heard of this symptom?

As noted by Leonardo, this isn't necessarily indicative of one specific thing - but it is this type of behaviour that can result when the CPU isn't happy. CPU unhappiness could be related to bad power from the PSU, a bad reset signal, battery acid damage on the CPU board, to something as simple as a bad EPROM on the CPU board.

The nice thing about the Chroma and Chroma Expander is that there really aren't a lot of exotic parts in them - and so if you find one that has all the mechanical bits and pieces (case/voice boards/panel, etc.) - then they're pretty much guaranteed to be repairable.

My $0.02 would be that as long as the unit is complete and otherwise in OK shape, it will be able to fixed - but the fact that it is not working would have to be factored in to what you think would be a good price to you.

Ken Ypparila [21030229] · Wed, 3 Aug 2011 17:56:13 -0700

I removed the crowbar from across the big cap on my Chroma and the same problem went away.

Paul DeRocco [21030230] · Fri, 5 Aug 2011 00:45:02 -0400

First, I'd check for proper DC voltages and no significant ripple on all the supplies. Then, I'd check the reset line from the power supply to make sure it is sitting at around 5V and not chattering on and off. Then, I'd reseat all cable connectors.

patch editor librarian?

Keith Hedger [21030607] · Fri, 5 Aug 2011 14:18:47 -0400

So I just got my chroma. I notice a lot of patches on the web site. I also notice that nobody seems to make patch editor/librarians anymore. So, I'll ask:

  • are there any patch editor/librarians out there?
  • how can I use the patches from the web site (I'm not familiar with any of the programs or formats talked about in the doc)

any suggestions?

Chris Ryan [21030691] · Fri, 5 Aug 2011 12:11:21 -0700

The Patches section of the site includes info on editors/librarians for iPad, Mac OS X, Mac OS, Windows, MS-DOS, Apple II, and Atari.

Chris Ryan [21030691] · Sat, 6 Aug 2011 13:42:43 -0700

So there are only two formats available on the Patch Downloads page, sysex and Galaxy. David's conversion tools are for converting to and from Galaxy, tape (audio), and sysex (and a couple for the EES interface); you won't need them. The patches in Galaxy format are identified by their file names; for example, factorygalaxy.sit. Different compression methods are used, to support users on different operating systems; so factory.zip and factory.tar.gz are both archives of the same sysex format factory patch file. (The .wav files for the factory patches are there as a convenience for those whose only option is the cassette interface).

Having written all that, I realize how confusing it must be. I'll try to simplify the page at some point. In the meantime, if you grab the following you'll have everything we've gathered over the years:

Hope this helps. Let us know if you have success with these.

control box layout sketch

Jesper Ödemark [21010135] · Sun, 07 Aug 2011 17:31:56 +0200

Hi list,

I spent some time today fiddling with the design for my dedicated (Doepfer Drehbank) Chroma controller. The original Drehbank is the standard boring grey type that Doepfer just love.

chroma_drehbankthumb.jpg

I plan to cover it in adhesive black film and then print this design on two clear sheets of overhead film, joining them at the middle.

chroma_lathe_testthumb.jpg

The knobs are also grey and hopefully I can track down thinner black knobs, maybe even with knob caps in the Chroma colour scheme. If all turns out well I might even add cherry end cheeks.

The two columns of knobs to the right correspond to eight input jacks at the back. I've thought about re-programming the Drehbank to allow all these eight to accept breath control and then map it to eight different destinations in the Chroma. More on this (a lot) later... The blank knobs are unused. I thought about removing them, but God knows what Dave and Sandro might add in the future. Can you even do scratch patches and bank select by CC? :)

The typeface isn't the best as this resolution, but you get the general idea. Feedback welcome!

Chroma on german Ebay

Jesper Ödemark [21010135] · Tue, 09 Aug 2011 09:51:33 +0200

I don't think I've seen this mentioned here: [eBay item #220822708077]

Incl EES midi etc. If already mentioned, please ignore. :)

Chris Ryan [21030691] · Tue, 9 Aug 2011 08:26:45 -0700

Thanks Jesper. Could you do a quick translation of the description for us, and ask the seller for the serial number?

Jesper Ödemark [21010135] · Tue, 09 Aug 2011 18:08:05 +0200

OK, here we go. I bet the germans on the list can iron out my high school mistakes. :)

"Rhodes Chroma the flagship of the analogue synthesizers

The Chroma is is a dreamlike collector's condition and can be tested in Hettstedt (Sachsen-Anhalt). No thermal problems, technically and cosmetically almost like new. With the Chroma comes a prototype of the EES MIDI Retrofit and a sturdy case. This EES Interface does not control SysEx!

Private sale - no returns or trades possible. The machine can be tested at pickup. Everything else that can be seen in the photos are NOT included in this auction. Questions? Call 03476-810301."

I'll contact him for the serial.

Jesper Ödemark [21010135] · Tue, 09 Aug 2011 20:15:14 +0200

Hi again Chris,

This is Chroma 21010303

Apparently not on the registry before and one of the very last in the european batch.

EPROM Set, Factory Patch Tape on eBay

Chris Ryan [21030691] · Fri, 12 Aug 2011 08:58:21 -0700

EPROM Set Rev 14, item #120762311569, USD$149.00. "The EPROMS are untested and being sold AS IS with no warranty or returns allowed."

eBay120762311569.jpg

Cassette Tape w Factory Presets, item #290598446061, USD$29.99. "The unit is 100% functional and in nice cosmetic shape as well."

eBay290598446061.jpg

Chris Smalt [21010280+] · Sat, 13 Aug 2011 16:00:53 +0200

*groan* I'm *this* close to offering jars of original air samples taken from my Chroma flightcases for USD$29.99 each.

Jack Colburne [21030142+] · Sat, 13 Aug 2011 19:47:45 -0400

ha!.. that's funny.

I just found a EPROM set that I have had for over 25 years, but assumed, because of the CC+, that no one would want them. Will be interesting to see if these sell.

hmm... they're also selling a TR-808 for $3000, a JP-8 for $7000, a Mini for $7000, and an OSCar for $4200. Cool. I am definitely in the wrong business.

CA3086 replacement

Luca Sasdelli [21010226] · Sat, 13 Aug 2011 13:56:03 +0200

Hi all,

which IC is a recommended CA3086 transistor array replacement? It seems that CA3046 should be better matched, while the current NTE912 [PDF] should be easy to find and cheap.

Any opinions?

Heinz Weierhorst [21010276] · Sat, 13 Aug 2011 14:28:56 +0200

Hi Luca.

The only difference between the CA3086 to the CA3046 is that the CA3046 has a matched difference pair of transistors. The NTE912 seems to be a clone of the CA3046. THAT CORP. offers a quad transistor array with large geometry transitors, ideal for Log/Antilog circuits but the have a different pinout and are hard to find.

Luca Sasdelli [21010226] · Sat, 13 Aug 2011 17:17:38 +0200

Thanks Heinz! Probably I'll get a few NTE912 from my supplier and I'll test them on some DVBs.

Paul DeRocco [21030230] · Sat, 13 Aug 2011 11:36:25 -0400

Believe it or not, you could probably get perfectly okay results by buying a bunch of 2N3904 transistors, gluing them together into pairs, and stuffing them into the CA3086 footprint (leaving out Z1E). For years, ARP made perfectly good expo converters out of "mismatched pairs" of 2N3904s and 2N3906s clipped together for thermal matching, and then just providing a wide adjustment range for the offset. Tying together 2N3904s out of the same lot should provide reasonably good matching, good enough for the auto-tune to take out.

Luca Sasdelli [21010226] · Sat, 13 Aug 2011 17:45:37 +0200

Hi Paul,

yes, I know those hard-matched pairs, as they are in my Odyssey II :) Anyway, NTE912s are quite cheap and the thermal coupling with tempco resistors would fit properly, therefore I'll try that way.

Doug Terrebonne [21030114] · Thu, 25 Aug 2011 20:49:56 -0700

I have some CA3046s now in stock if you want the real thing. :)

Luca Sasdelli [21010226] · Fri, 26 Aug 2011 08:02:32 +0200

Good! Well... of course the price would be the most relevant info :)

working Chroma not working after transport--- any advice?

Ben Vehorn [21030757] · Sat, 13 Aug 2011 21:55:13 -0400

Hi all,

I just traded my Chroma away (I'm sure I'll regret this!) and the new owner lives 3 hours away so we met halfway for an in-person swap. It has had the CC+, SPSU and CPS AT upgrades all within the last 18 months and has had zero problems since upgrading the PS and CPU. I've been playing it a lot this week with no issues and was saying my final goodbyes to it this morning before leaving and it was working fine.

The new owner just got it home and it doesn't seem to be producing any sound from the high mono output except for very faint white noise, and really loud noise from the XLR output. He opened it to check to make sure no cables/connectors/voice cards vibrated loose and it didn't look like they had. It sounds like it's booting up normally and is not showing any errors on boot.

He's tried the set split diagnostics (reset, mute/unmute, etc) and it didn't fix it. He's able to change patches, change parameters, go into the diagnostics mode, use all the membrane switches, etc... everything appears to be working, just no sound.

One weird thing is that the tapper solenoid was set to off when I left this morning but it was set to on when it arrived. I realize now that I didn't set the rear memory lock switch to on, would this make a difference? Could the memory have gotten scrambled somehow by moving it and, if so, is there a "harder" hard reset we can try?

If UPS or Fedex had been involved I'd suspect damage, but we were both very careful with it and I'm at a loss as to why it wouldn't be working.

Does anyone have any ideas or suggestions as to what could go wrong during a simple, gentle, in-person delivery? We're going to swap back if we can't get it figured out in a couple of days.

Luca Sasdelli [21010226] · Sun, 14 Aug 2011 05:40:48 +0200

Hi Ben,

if it does autotune (and I guess yes because of not mention), all logic and voice boards ass'y is okay. Did the new owner try to issue a SetSplit39 to create a scratch patch? If this doesn't sound, I suspect a failure on EQ board (perhaps a VCA?). Please ask him to issue SetSplit5, and check if output 3 does produce some audio: in this way, a different VCA and ground isolation buffer is used, and the whole muting+tone control is not used.

Michael Dykehouse [21030757] · Sun, 14 Aug 2011 00:47:34 -0400

Keys not triggering

Hello:)

Just traded some gear for a Chroma that has all of the major updates (cc+, new power, poly aftertouch)and was working this morning (I didn't test it but I trust the guy who owned it before me). Anyways, the drive back from Ohio to Michigan must have done something. It powers up, doesn't have any errors, but the keys aren't making any sounds. I have tried all of the outputs and I just get a slight hiss with the volume maxed. I have tried everything, midi local is on, tried split 50, all of the splits that would have any effect, opened it up and didn't notice any cable weirdness. Any ideas? I was so excited and now...I need help! Thanks for any tips and all the best, Mike Dykehouse

Michael Dykehouse [21030757] · Sun, 14 Aug 2011 00:55:55 -0400

(no subject)

Oops Hello Ben! Thanks for posting! Hope we can figure this out:)

Michael Dykehouse [21030757] · Sun, 14 Aug 2011 01:57:23 -0400

(no subject)

Also , when in set/split 37 I don't see anything blinking when I press the keys which makes me think this is the problem. Which connections should I focus on to make sure everything is connected correctly internally for the keyboard to work?

Luca Sasdelli [21010226] · Sun, 14 Aug 2011 12:55:15 +0200

Re: (no subject)

Hi Michael,

did you make those test I wrote in my previous email to list? What if you issue SetSplit39, then connect amp to Output 3 and select SetSplit5?

Ben Vehorn [21030757] · Sun, 14 Aug 2011 18:42:44 -0400

Hi Luca,

Thanks for the info. I think there was some sort of posting delay going on last night because it looks like he posted about it right after me.

This morning he tried the scratch patch and tried setting it to output 3 with no luck.

Since it's clear that this must be some sort of hardware problem, we decided to meet up again and trade back and I now have the Chroma back in my hands.

I've gotten the same results as him with all the diagnostics tests and still no sound. One thing I did notice is that when I push the mid EQ slider up the noise floor gets slightly louder and more midrangey, so at least the output op-amp for the tone control seems to be functioning.

I've got it open and can't see any signs of trauma or loose connectors. The only thing I noticed is that the CPS kit had come slightly away from the mounting rail in the middle where the PC board is and when I pushed down on the connection at the other end (at J22) it was the slightest bit unseated, though this didn't fix anything.

I'm going to go through it with a flashlight and magnifying glass but if anyone can think of anything I should check I'd greatly appreciate it!

Thanks.

David Clarke [21030085++] · Sun, 14 Aug 2011 19:00:45 -0400

I'm going to go through it with a flashlight and magnifying glass but if anyone can think of anything I should check I'd greatly appreciate it!

You can put the CC+ into voice-watch mode (Set Split-37). If with a scratch patch you see LEDs illuminate in the small LED display when you press keys, they the key presses are getting into the Chroma.

If you don't see any key stroke information, confirm that the unit is set the 'Chroma' mode vs. 'Expander' mode - otherwise the keystroke information will be ignored. To do so, that'd be [Set Split-36], [P22]. You'll want to see Chro and not Pndr. If you see Pndr, move the slider to see the Chroma setting.

If you do see key stroke information with Set Split 37, a scratch patch and keypresses, then we'd be looking to see if something is affecting the volume output, etc.

Let us know how you make out.

Ben Vehorn [21030757] · Sun, 14 Aug 2011 19:09:34 -0400

Thanks Dave,

I dialed up a scratch patch and then did Set Split 37--- no activity on the display.

Sounds like we're getting somewhere now!

I checked and it's in Chroma mode and says EP in the program number display.

One thing I mentioned last night but will restate here because it might be relevant--- I forgot to set the memory lock/protect switch to on before moving it. When it left my house the tapper option was disabled and when it arrived to him it was engaged. I'm not sure if this points to anything, but it's a bit odd as I don't know how it would have been reset unless something changed in the memory/preferences during transport.

Ben Vehorn [21030757] · Sun, 14 Aug 2011 19:23:32 -0400

PS--- I just double-checked all the connections internally, particularly the keyboard. It looks like a single ribbon cable going from the Stack Switch board to the middle front panel board, and from that board on to the voicecard motherboard... correct? These connections appear secure.

Paul DeRocco [21030230] · Sun, 14 Aug 2011 19:29:54 -0400

One thing I mentioned last night but will restate here because it might be relevant--- I forgot to set the memory lock/protect switch to on before moving it. When it left my house the tapper option was disabled and when it arrived to him it was engaged. I'm not sure if this points to anything, but it's a bit odd as I don't know how it would have been reset unless something changed in the memory/preferences during transport.

Red herring. The Lock switch is just a switch that the firmware can read. In the original Chroma, if it was set, the firmware would refuse to respond to the STORE switch. I assume the replacement CPU board does something similar. There is no direct connection between the switch and the CMOS memory.

Ben Vehorn [21030757] · Sun, 14 Aug 2011 19:48:51 -0400

Okay, cool, just wanted to make sure.

A couple of other things I've noticed...

  • it's not responding to external midi either. I have the CC+ breakout box with the indicator lights and get no activity on the input
  • if I crank the volume, there are a few patches on which I can hear a high-pitched drone very faintly. The tuning and (in most cases) mod levers affect the pitch of it but is not changed by playing notes on the keyboard.

RJ Krohn [21030455] · Sun, 14 Aug 2011 18:41:38 -0700

sorry about your troubles, ben. sucks. i'd try removing all the voice boards except one and see if the tuning errors match the voice board absences?

curious, what were you gonna trade for?

David Clarke [21030085++] · Sun, 14 Aug 2011 22:20:54 -0400

... When it left my house the tapper option was disabled and when it arrived to him it was engaged. I'm not sure if this points to anything, but it's a bit odd as I don't know how it would have been reset unless something changed in the memory/preferences during transport.

The tapper setting is just a setting in the memory. As noted by Paul, the memory switch doesn't actually prevent (in hardware) access to the RAM; rather, it is just an input to the software to prevent it from doing certain things.

The NoVRAM used on the CC+ should maintain its settings until/unless changed by the user. There isn't normally expected to be changes in the settings (like the tapper setting) unless commanded to do so, or unless there are problems.

If one setting has changed, then others may have too. It certainly wouldn't be a bad idea to check all of the settings that get stored. It makes sense that you wouldn't get any sound out from the keyboard (if you don't see any key activity in voice-watch mode (Set Split 37). That said, that shouldn't affect in any way behaviour from MIDI - but other settings from set-split 36 could (e.g., MIDI channel changed, MIDI mode changed, etc.)

It will be very odd if everything else seems to work fine - but nothing can be trigger from either the keyboard or MIDI (as both take different internal paths).

Ben Vehorn [21030757] · Mon, 15 Aug 2011 10:44:07 -0400

There are no tuning errors, everything boots up like normal and the front panel responds to all key-presses and set-split commands... it's just not making any sound. No visible trauma, no loose connections, no errors, but no sound.

I was trading for some modular stuff (Cwejman S1 Mk2 and some eurorack modules/case) as I'm trying to expand my modular system. I do love the Chroma, though, and think maybe I dodged a bullet here. Once I get it working properly again I'll likely keep it. Having seen the prices of all the other vintage polys go through the roof (JP8 for 6K? CS80 for 18K??? crazy!) I feel like the Chroma, though much more expensive now than it was a few years ago, is currently undervalued by way of comparison and if I get rid of it I'll be permanently priced out of the market when people realize this and prices shoot up.

Ben Vehorn [21030757] · Mon, 15 Aug 2011 11:34:13 -0400

Okay, I seem to have gotten a little further. I just did a set-split 36 and the midi channel had been changed so I changed it back and now it's responding over midi, though the keyboard is still not triggering it. So now it's clear that somehow the preference settings got changed just by moving it.

Here's the weird part, I'm in programming mode (EP shows on display) and have the Parameter Select button lit up. When I try to go to any other parameter other than 1/Base midi channel, it stays on on parameter 1... I'm trying to check the local on/off and can't get to it. Even weirder, when I hit parameter 18 (edit MCM) it stays on parameter 1 but changes the value to 17, which, as far as I can tell shouldn't be an option since there is no midi channel 17. If I press it again, it changes the midi channel back to 1. If I press button 19, it changes the midi channel to 3 and then back to 1 if I press it again. All of the numerical membrane switches are working fine as far as selecting patches and parameters when I'm not in programming mode. Am I doing something wrong?

Any ideas on where I can go from here? One thing I forgot to mention is that it's running firmware 2.13. I'm just speculating here and don't even think this is possible, but since some of the preferences have randomly changed is it possible that there could have been some sort of OS or stored memory corruption?

Thanks,

Ben

Ben Vehorn [21030757] · Mon, 15 Aug 2011 11:48:15 -0400

Okay, I'm an idiot and realized I needed to be in Program Select while in programming mode to get to these. Local control is turned on. I did an MCM Init and am still not getting a reaction from the keyboard, but I am over midi.

Heinz Weierhorst [21010276] · Mon, 15 Aug 2011 18:42:54 +0200

Hi Ben.

First question: Do you have a scope?

If not, make a little shielded cable with a 1/4 inch jack at one side. At the other end solder a wire to the shield and then via a cable (not to short) to a crocodile clamp. The "hot" line should be connected to to a small tip just like it's used for voltmeters and so on.

Next you need a little (guitar) amp or similar. Plug cable in into the amp with volumepot in min. position. The crocodile clamp to the ground point of the rear panel (the thick green wire coming from chanel motherboard). Set the Chromas preset to a programm with squarewaves on both oscillators (bank 1, preset 17 = wooden pop) and press autotune.

Do not hit any keys. The tip of the cable should lead to one of the test point of the dual voiceboard (that big holes near the two trimpots on dual voiceboard).

Switch on the amp and turn very carefull the volumepot up, it could get very loud! Now you should hear sound, a C = 262 Hz on each testpoint. Press a bundle of keys and listen if the oscillators have changed pitch. If so, the keyboard scanner works. Let me know the result.

RJ Krohn [21030455] · Mon, 15 Aug 2011 10:14:33 -0700

I was trading for some modular stuff (Cwejman S1 Mk2 and some eurorack modules/case) as I'm trying to expand my modular system. I do love the Chroma, though, and think maybe I dodged a bullet here. Once I get it working properly again I'll likely keep it. Having seen the prices of all the other vintage polys go through the roof (JP8 for 6K? CS80 for 18K??? crazy!) I feel like the Chroma, though much more expensive now than it was a few years ago, is currently undervalued by way of comparison and if I get rid of it I'll be permanently priced out of the market when people realize this and prices shoot up.

yea, i'd DEF hold on to it if it ends up working again.

one thing i've been super stoked on lately is that of the cs80, chroma, and T8, the chroma is the only synth i have that responds to Poly AT. the combo of "cool vintage sound" and "modern interfacing capabilities" is really really nice.

Ben Vehorn [21030757] · Mon, 15 Aug 2011 14:21:05 -0400

Hi Heinz,

No, I don't have a scope.

I tried your suggestion and was able to get the C drone but the oscillators didn't change pitch when I hit the keys. Does this mean it's not scanning the keyboard properly? If so, what would be the likely culprit?

Thanks,

Ben

Heinz Weierhorst [21010276] · Mon, 15 Aug 2011 21:53:39 +0200

Hi Ben.

O.K. All 16 oscillators produce that C? Is the Chroma set to Chroma or Expander mode? If it is set to Chroma you're in trouble with the keyscanner. Check that flat cable from the keyswitches to the I/O board first.

Ben Vehorn [21030757] · Mon, 15 Aug 2011 17:10:08 -0400

Hi Heinz,

I checked continuity on the ribbon cable from the stack switch board to the I/O board and all pins test good. I then tested the power rails on the stack switch board and noticed that there is no power on the +12V rail of the left stack switch board... the right board (the one that connects directly to the I/O board tests fine on power rails (5.02V and 11.99V).

So, for some reason the left stack switch board isn't getting power to the 12V rails. I checked continuity between the thin ribbon cable that jumps the 2 boards together and all pins tested fine. Is there something that can fail on the stack switch board that could short out the entire 12V line on one side only? Thanks again for the help, it's really nice to have experts who are willing to help me out!

Dave Bradley [16330135] · Mon, 15 Aug 2011 16:19:58 -0500

Shorted bypass cap?

Ben Vehorn [21030757] · Mon, 15 Aug 2011 17:40:06 -0400

Are you talking about the ceramic capacitors, one on each of the stack switch boards?

Another thing I noticed is that I get continuity between the 5V and ground rails on both boards, is that normal? I'm not getting between the 12 V rails from board to board am assuming this is relevant as well. I looked at the schematic and wasn't really clear as to the path it takes but I'm not very experienced with reading them.

Thanks,

Ben

Paul DeRocco [21030230] · Mon, 15 Aug 2011 18:18:31 -0400

Another thing I noticed is that I get continuity between the 5V and ground rails on both boards, is that normal?

The "continuity" you're seeing is probably just the bypass caps being gradually charged by the meter current.

I'm not getting between the 12 V rails from board to board am assuming this is relevant as well. I looked at the schematic and wasn't really clear as to the path it takes but I'm not very experienced with reading them. Thanks, Ben

+12V doesn't go to the left board. All it has on it is a 74LS145 decoder, which only needs +5V. The +12V is only for the LM339 quad comparators.

Ben Vehorn [21030757] · Tue, 16 Aug 2011 00:10:36 -0400

I guess that's a relief since it means the stack switch would be getting the proper power. So if the problem is with the stack switch assembly but it's not with the connector cable or the power rails, what could it be? If one chip or resistor went down, would it take everything down with it?

Sorry to keep bugging everyone with my problems but I really want to get this figured out! I've made so many posts about this already that I think it might be worthwhile to do a quick bullet-point rundown of where I'm at.

  • No problems with booting and no voice errors. SPSU power and CC+ were installed ~15 mos ago and its had no issues until now, which happened after a physical move (though not shipped). At least one or two preferences (tapper on, possibly midi channel) somehow randomly changed during the move.
  • responds over midi but won't respond to internal keyboard, and shows no activity in voice watch mode
  • Local midi is set to on, Chroma is set to Chroma (not Expander) mode
  • continuity between right stack switch board and I/O board is solid on all connector pins
  • continuity between right stack switch board and left stack switch board is solid on all ribbon connector pins
  • +5V power rail on left stack switch board is good, and +12V and +5V rails on the right board are as well

Again, the move of this instrument was very gentle and it didn't experience any trauma. All the connectors seemed well seated when I got it back and it seems odd that there would be a hardware failure while riding in the back of my car. Is there any other preference that could be accidentally set that could cause it to ignore the keyboard? Is there any sort of a "harder" hard reset that completely resets everything to original CC+ settings? And, if not, how would I go about troubleshooting the stack switch assembly?

Thanks,

Ben

Paul DeRocco [21030230] · Tue, 16 Aug 2011 00:30:11 -0400

I guess that's a relief since it means the stack switch would be getting the proper power. So if the problem is with the stack switch assembly but it's not with the connector cable or the power rails, what could it be? If one chip or resistor went down, would it take everything down with it?

Well, it can be pretty hard to figure these things out with minimal tools.

One possibility is that something has crashed the keyboard scanner. With a scope, that would be pretty easy to see. You could also test it by touching an audio cable to the top of one of the keyswitches, plugged into something with the volume turned way down, to see if there's a strong 1KHz pulse wave there.

If there isn't, it's also possible that the scanner is working, but that the interrupt to the main CPU isn't. In that case it would scan until you hit the first key (or maybe it's two keys), and then stop. This can happen if there isn't continuity on the KINT line on J9-14, one of the flex strips from the I/O board to the CPU board.

Given that latter possibility, the first thing you should do is unseat and reseat both of those flex strips. In general, it's always a good idea to reseat connectors, since they're a common cause of failures that are easy to fix.

Heinz Weierhorst [21010276] · Tue, 16 Aug 2011 13:26:40 +0200

Hi Ben.

When you move the data entry slider up and down, do the values change? If so, the key scanning computer is doing something. The computer puts out a signal called ALE (adress latch enable). This signal is also used as a clock for the ADC (analog to digital converter). The data slider is connected to that ADC.

Another thought is J9, that ribbon cable from the main computer to I/O board. Check if J9-12 is connected to Z31-2 and J19-13 is Z31-3. Check also J10.

Keith Hedger [21030607] · Tue, 16 Aug 2011 08:01:52 -0400

working Chroma not

I've recently returned to the Chroma, but does the MIDI implementation have a 'local' mode? There are some implementations that support local mode allowing the local keyboard to ONLY send midi out. Don't know if the Chroma implementation(s) have this or not....

David Clarke [21030085++] · Tue, 16 Aug 2011 11:16:34 -0400

... Is there any other preference that could be accidentally set that could cause it to ignore the keyboard?

No - not really. Since the keyboard works from MIDI that rules out bad settings for volume, etc. If the only bad behaviour currently occurring is the lack of triggering from the keys, then the appropriate debug would be to trace through the signal path from there to see where the value is lost (e.g., things like the keyboard scanner, KINT, as noted by others).

Whether the problem is mechanical in nature (e.g., a chip with a bent pin that was making contact for the the past 15 months, now slightly shaken loose by the travel) or electrical - following the signal thought to see where the signals aren't right anymore will let you know.

... Is there any sort of a "harder" hard reset that completely resets everything to original CC+ settings?

There is no key sequence that will do this for you.

A complete reset of all settings (e.g., all contents of the NoVRAM on the CC+) can be done by installing an 'initialization' EPROM. To use that, you'd need to have the capability to burn that EPROM there.

The settings for the CC+ itself are the ones you see displayed when you issue [Set Split][36], and so if you've stepped through all of those settings and they all look fine, then those are the settings the interface will use. You can always change the values and re-save them to something else, if you want to ensure that the settings are active. The other stored values are the ones used by the original Chroma (e.g., tapper settings, Chroma interface settings, etc.) - and those would be controlled by the original Chroma key sequences (e.g. [Set Split][9], [Set Split][10], etc.)

Luca Sasdelli [21010226] · Tue, 16 Aug 2011 17:26:24 +0200

A complete reset of all settings (e.g., all contents of the NoVRAM on the CC+) can be done by installing an 'initialization' EPROM. To use that, you'd need to have the capability to burn that EPROM there.

Hi David,

do you think there is any way to include the init code within the current firmware? Is it a matter of EPROM size or what?

I guess it would be of some help in "desperate" issues (if any...) :)

Ben Vehorn [21030757] · Tue, 16 Aug 2011 11:27:39 -0400

Hi Heinz,

Yes, the data entry slider is working as normal, I can use it to change parameters with no problem. Everything other than the keyboard is working completely as normal.

I tested continuity on all points of J9 and J10 on the I/O board to the CC+ board and everything was fine. Is this what you meant? I couldn't find a Z31 on the CC+ board.

I went ahead and completely reseated all the cables on the I/O and CC+ boards and it didn't fix anything.

Heinz Weierhorst [21010276] · Tue, 16 Aug 2011 17:35:07 +0200

Hi Ben.

Z31 is on the I/O board. It's the key scanning processor.

Ben Vehorn [21030757] · Tue, 16 Aug 2011 11:50:54 -0400

Hi Paul,

I might be able to get loan of an oscilloscope and have a frequency counter on my Iphone, though I can't hook a test lead up to it. What additional tools would I need to debug this further? A friend of mine builds guitar pedals for a living and has a nice workshop with lots of tools, so I can probably get access to what I need as long as it's not too esoteric.

I verified continuity where the base of the connector meets the I/O between all pins of J9/J10 and the CC+ board. I didn't go so far as to reseat them as they seem somewhat fragile, but I'll try it anyway just to see if it helps.

I touched an audio cable to the tops of some keyswitches and got a signal it seems to be digital hash and not particularly loud. I recorded a brief snippet at what would normally be unity gain for the Chroma and posted it.

Ben Vehorn [21030757] · Tue, 16 Aug 2011 12:15:24 -0400

Z31 is on the I/O board. It's the key scanning processor.

Ah, okay, that makes sense then.

Pin 2 on Z31 is showing continuity to pins 1-8 on J9 (the lowest 8 pins when the top is flipped open) and no other pins on H9 or J10. I also noticed that pin 1 on Z31 has continuity to the same 8 pins.

I must have bad eyes because I can't find J19 anywhere, I've gone over the board several times with a flashlight and studied the IO Assembly pdf from the service manual... where should I look for it?

Lars Johansson [21030632] · Tue, 16 Aug 2011 18:58:49 +0200

Re: working Chroma not

I've recently returned to the Chroma, but does the MIDI implementation have a 'local' mode? There are some implementations that support local mode allowing the local keyboard to ONLY send midi out. Don't know if the Chroma implementation(s) have this or not....

The CC+ has Local On/Off.

David Clarke [21030085++] · Tue, 16 Aug 2011 13:52:57 -0400

... do you think there is any way to include the init code within the current firmware? Is it a matter of EPROM size or what?

The number of control settings are very small, and they could be included in the firmware - but then again, you have full control over that init by going into the [Set Split][36] interface and setting the values.

The other things the INIT EPROM code does is to fill in all of the default programs. The init code (including a duplicate copy of all the default programs) would be too large to fit in the main CC+ firmware image in addition to the operational code that is there so the full init can not be combined with the operational image (hence the need for a separate EPROM image).

Heinz Weierhorst [21010276] · Tue, 16 Aug 2011 20:09:49 +0200

I must have bad eyes because I can't find J19 anywhere, I've gone over the board several times with a flashlight and studied the IO Assembly pdf from the service manual... where should I look for it?

Hi Ben.

Your eyes are o.k. but mine not. It shouled read J9 and J10.

Ben Vehorn [21030757] · Tue, 16 Aug 2011 14:55:56 -0400

Hi Heinz,

I checked this and realized that before I was reading the pins the wrong way before on Z31. Z31-2 is showing continuity to J9-12 and across to the CC+ board... but Z31-3 is *not* showing continuity to J10-13 although it is to J9-13... is this what you meant?

I pulled/reseated Z31, J9 and J10 (and all other connectors on the IO board for good measure) but it didn't help. I'm testing perfect continuity between J9/10 and the CC+ board.

Ben Vehorn [21030757] · Tue, 16 Aug 2011 17:31:37 -0400

After spending all day looking at the service manual and going back and re-reading everyone's advice it seems likely that the keyboard scanner has to be the culprit. I reseated both Z31 and Z33 and they're snug.

When touching the audio cable to the tops of the keyswitches I get noise but it seems to be full-spectrum and isn't very loud. Is this evidence of the keyboard scanner being down? If so, and so far all the physical connections have tested good for continuity, would this mean I would need to replace either/both Z31 or Z33?

Is there any way I can test whether these are functioning properly, or would it be wise to just try and hunt for replacements?

Z31 isn't listed in the parts list (except for a reference to the IC socket that holds it and Z33 is listed as "IC EPROM PROGRAMMED KEYBOARD SCAN". Are there people out there who have access to the code on these or am I screwed?

Thanks for the help everyone, I'll have to make a donation to the site once I get this all figured out.

Luca Sasdelli [21010226] · Tue, 16 Aug 2011 23:46:34 +0200

Very interesting trouble.

Anyway, some time ago I was thinking to purchase a low-cost scope and I did find this one: [eBay item #390312463471, ARM DSO Portable Tiny Digital Scope DSO201 DIY Kit Nano].

It features 1MHz bandwidth... not that much, but maybe acceptable for audio purposes and measures. (Then I've bought a 60MHz Owon palm scope instead).

Luca Sasdelli [21010226] · Tue, 16 Aug 2011 23:50:18 +0200

The init code (including a duplicate copy of all the default programs) would be too large to fit in the main CC+ firmware image in addition to the operational code that is there so the full init can not be combined with the operational image (hence the need for a separate EPROM image).

Ok, thanks!

Paul DeRocco [21030230] · Tue, 16 Aug 2011 23:08:28 -0400

I might be able to get loan of an oscilloscope and have a frequency counter on my Iphone, though I can't hook a test lead up to it. What additional tools would I need to debug this further? A friend of mine builds guitar pedals for a living and has a nice workshop with lots of tools, so I can probably get access to what I need as long as it's not too esoteric.

If you can borrow a scope, and know basically how to use it, do that. That'll probably be all you need.

I touched an audio cable to the tops of some keyswitches and got a signal it seems to be digital hash and not particularly loud. I recorded a brief snippet at what would normally be unity gain for the Chroma and posted it.

This suggests the scanner isn't scanning. Did you listen right after turning the unit on, without playing any keys? My earlier point was that if the handshaking between the keyboard scanner and the main CPU is broken, the scanning will work until you've played a note, or perhaps two, after which the keyboard scanner will hang waiting for the main CPU to respond. That could be an important clue.

Heinz Weierhorst [21010276] · Wed, 17 Aug 2011 13:43:15 +0200

Hi Ben.

First check the signal !KMASK. It's on Z49 (74LS10) pin 10 on I/O board. With a voltmeter measure if there is appr. 5 volts. Then hit AUTUTUNE. While autotuning this voltage must go to a low level.

But when autotuning has finished it must go high again. When the signal is low all the time then there is a fault who could be caused by the circuit or by wrong parameters, local off and so on.

I will do some additional measurements on my Chroma and let you know the results.

Ben Vehorn [21030757] · Wed, 17 Aug 2011 11:01:59 -0400

This suggests the scanner isn't scanning. Did you listen right after turning the unit on, without playing any keys? My earlier point was that if the handshaking between the keyboard scanner and the main CPU is broken, the scanning will work until you've played a note, or perhaps two, after which the keyboard scanner will hang waiting for the main CPU to respond. That could be an important clue.

Hi Paul,

I ran this test again, this time right after booting and before playing any keys. I got the same noise before and after touching the keys, it didn't seem to change.

Ben Vehorn [21030757] · Wed, 17 Aug 2011 11:03:43 -0400

First check the signal !KMASK. It's on Z49 (74LS10) pin 10 on I/O board. With a voltmeter measure if there is appr. 5 volts. Then hit AUTUTUNE. While autotuning this voltage must go to a low level.

But when autotuning has finished it must go high again. When the signal is low all the time then there is a fault who could be caused by the circuit or by wrong parameters, local off and so on.

Hi Heinz,

I ran this test and showed a steady +5V on pin 10 of Z49. However, it did not droop when I ran the autotune routine. It sounds like this is not normal?

Heinz Weierhorst [21010276] · Wed, 17 Aug 2011 17:20:03 +0200

Hi Ben.

No, that isn't normal. I've checked it on my Croma and !KMASK goes low while autotuning and after that high. Just make an additional test at Z36 pin 18. It's a "high" signal but must go low when hitting a key. It is called A/R flag.

Paul DeRocco [21030230] · Wed, 17 Aug 2011 11:20:41 -0400

I ran this test again, this time right after booting and before playing any keys. I got the same noise before and after touching the keys, it didn't seem to change. Thanks, Ben

It sounds like the keyboard scanner might be dead. It could be that its EPROM has started to drop bits. But whatever it is, it sounds less and less like something that can be figured out by analyzing the symptoms, and something that requires examining signals in detail with a scope.

Did you look at KINT with a meter? It's supposed to sit high normally, go low when a key is pressed, and then go high again when the main CPU reads the key information. You normally wouldn't see it going low on the meter, but if it goes low and stays low, that would at least indicate that the keyboard scanner is probably working, and the problem is in the handshaking between the two CPUs.

Heinz Weierhorst [21010276] · Wed, 17 Aug 2011 17:27:19 +0200

I ran this test again, this time right after booting and before playing any keys. I got the same noise before and after touching the keys, it didn't seem to change.

Hi Ben.

Do that test again. The tip to a upper contact of a keyswitch and then hit that key. You should hear a loud tone. Try on different keys. If so, the keyscanner is working. What you was hearing before is some digital crosstalk.

Ben Vehorn [21030757] · Wed, 17 Aug 2011 11:31:39 -0400

Hi Heinz,

I retested the !KMASK with the same result, it's a steady 5V and doesn't droop when autotune is engaged. I tested Z36-p18 and got a steady 1.49V that didn't change when I hit a key.

I did some more reading of the service manual last night and found that Z31 is an old Intel 8039 CPU that computes the keyboard scanning and am guessing that maybe this is a likely suspect. Is it possible that this somehow went bad? They seem to be cheap (Jameco has them for <$4) so I went ahead and ordered a replacement just in case, a chip swap seems like an easy and cheap test to do. But I will be waiting for it to arrive for a few days, so if you think of anything else I should be testing, please let me know!

Ben Vehorn [21030757] · Wed, 17 Aug 2011 11:39:39 -0400

Do that test again. The tip to a upper contact of a keyswitch and then hit that key. You should hear a loud tone. Try on different keys. If so, the keyscanner is working. What you was hearing before is some digital crosstalk.

I tried again, this time paying attention to which actual key I was playing. I get the digital noise (although it seems like it has a strong fundamental) after turning on and before hitting a key. While the key is held down, there is silence. When I release the key, the noise is back and, perhaps it's just my imagination, but it seems like the noise has an additional high frequency harmonic after I press the key the first time.

Heinz Weierhorst [21010276] · Wed, 17 Aug 2011 18:42:22 +0200

Hi Ben.

This is strange behaviour. The key scanner didn't work. But a next check: With the tip of the audio cable go to Z34 pin 18,16,3,14,12,7 and 9. Do you hear any sound? If not, the scanning computer hangs. If yes, just check Z34 pin 1 and 19 with a scope. There must be a small low going pulse coming out Z31 pin 8 (!RD=read). If this pulse is present go to Z34 pin 2,4,17,6,15,8,13 and 11. There should be squarewaves. Also test if on Z31 pin 4 there is a constant "high" (!RESET). With a scope go to Z31 pin 2 and 3. There must be a high frequency = 8Mhz on both pins.

Ben Vehorn [21030757] · Wed, 17 Aug 2011 17:14:50 -0400

Hi Heinz,

I don't get any audio coming off of those Z34 pins. Would that mean this chip is bad?

Heinz Weierhorst [21010276] · Thu, 18 Aug 2011 14:03:38 +0200

Hi Ben.

That could be normal when no key is detected, but I don't believe so. With a working computer there must be always some "traffic". From now on it's better to have a scope So check if on Z31 pin 9 there is short low going pulse. The signal is called !PSEN (program store enable). With this the scanning computer reads the eprom. The contents of the eprom tells the computer what he has to do. When the eprom is empty or contains wrong data the computer does nothing or nonsens. May be the 8039 or the eprom are faulty. But there are so many other solutions. I will do some measurements on my Chroma next.

Ben Vehorn [21030757] · Thu, 18 Aug 2011 08:35:12 -0400

Hi Heinz,

I've ordered a replacement 8039 and it should be arriving today. Since this seems like it could be a likely suspect, I'll go ahead and replace it first since it will be a quick and easy test. If it doesn't solve the problem I'll borrow a scope and run the tests you suggested. I'll let you know once I've replaced the 8039 and whether it fixes the problem.

Paul DeRocco [21030230] · Thu, 18 Aug 2011 20:50:11 -0400

Listening with amp to the keyboard scanner is not very helpfull 'cause only a bat could hear something. Most frequencies are to high.

The keyboard scanner scans at about a kilohertz, as I recall.

Heinz Weierhorst [21010276] · Fri, 19 Aug 2011 15:20:42 +0200

Hi Paul.

That's right, but on the databus of the 8039 there is much faster "traffic". I don't believe it's the scanning computer itself but something outside. Because ALE is active the computer is doing a job but did he do right? May be the handshaking circuit isn't working proper and so on. The next information I need are the Pulses on KA lines active? BTW. The note latch Z37 is 7 bit wide but only 6 bits are needed. Was there a plan to have a larger keyboard? Or is it so that 0 is an unwanted number? 0 to 63 or 1 to 64?

Chris Ryan [21030691] · Fri, 19 Aug 2011 08:00:19 -0700

Was there a plan to have a larger keyboard?

It seems so; see "Were there any plans (besides the Polaris) for future designs? What about the rumoured 88-key version?" in the Phil Dodds/Tony Williams interview.

Ben Vehorn [21030757] · Fri, 19 Aug 2011 12:02:36 -0400

Hi,

Unfortunately I'm at an impasse here... it turns out that my friend doesn't have a scope after all. It looks like the next step would be for me to either buy one (which I'm sure would prove useful in the future) or to take the Chroma to a tech. I've emailed Wes Taggart to see what his schedule is like, if it's something I can get turned around quickly I might just take it to him.

Regarding the scope... I'm looking at a Tektronix 2230 dual trace 100mHz scope on my local Craigslist. Can anyone tell if this is a decent scope and whether it would would be sufficient for most audio electronic applications? The price is a bit higher than the Ebay avg for this model, but it's local and he says he's willing to take offers... here's the ad: [posting ID 2508967929].

Pictures from the posting:

craigslist2508967929.jpg

So, in lieu of my being able to move forward at this moment, I'm going to do a "thinking out loud" rundown of where I'm at right now and ask some questions:

  • not responding to internal keyboard, everything else is fine and it responds over midi. No errors whatsoever. New SPSU, all lights are green and PS tests 14.99V and 5.05V.
  • I've ruled out Chroma settings (local, keyboard alg, mode, etc)
  • Set Split 37/show voice allocation shows nothing via internal keyboard, responds properly to external midi. We have now established that the Keyboard Scanning is not happening properly.
  • I can't find any loose connectors, and have reseated all the connectors on the IO boardSet
  • I've verified continuity on all pins between IO and Stack Switch boards, between the 2 Stack Switch boards, and between the IO and CC+ boards. The Stack Switch board power rails are all normal.
  • I've swapped out the socketed Intel 8039 at Z31 and that didn't fix the problem
  • Okay, so at this point I need a scope to do further tests. It seems reasonable at this point that the problem is either a bad component or solder joint on the IO board. Today I will remove the IO board and check the solder side to make sure that all pins of Z31 and Z33 are properly soldered with no cold joints. Looking at the block diagram, the keyboard goes into the Scanning computer to the CPU, and via a separate line to Keyboard Interrupt the CPU. The scanning computer seems to consist of 2 parts, the 8039 itself and the EPROM that contains the scanning code. The 8039 itself should be okay since I swapped it, so I think that would narrow it down to either a bad trace, a problem with the EPROM, or a problem with the keyboard interrupt.
  • is it possible that the EPROM has gone bad, or has somehow dumped the code? I've never heard of this happening but wonder if it's a possibility. If so, how would I obtain a replacement and, since it's socketed, would this be a worthwhile (hopefully) cheap thing to try?
  • how does the keyboard interrupt work? Does it just send a pulse down a line from the keyboard to the Scan CPU? I know I need a scope to test this, but could I somehow test the physical continuity down this line to make sure it's okay? If so, where would I measure this?
  • is there a piece of the puzzle I'm not thinking of here? Perhaps the RAM between the CPU and EPROM?

Luca Sasdelli [21010226] · Fri, 19 Aug 2011 18:24:25 +0200

Hi Ben,

the Tektronix is a luxury instrument, and the price you show is great; anyway, it's an old one, and it's a quite massive. As mentioned earlier, to use it in audio range I'd choose a palm-size one, like the DSO Nano 201v2 at 89US$

On eBay you'll find the old model at a pricing of 50 US$ or so. It has only 1MHz sampling clock, thus per Nyquist theorem is 500kHz bandwidth: you'll see a bit "rounded" square waves, but for fautfinding should be okay. Moreover it measures duty-cycle (DVB adjustment), frequency, period, voltage etc.

The quad-trace model has two 72MS/sec analog channels, thus it has 36MHz bandwidth; on eBay around 180US$

Otherwise you can look to Owon, Atten, Rigol etc... ex. [eBay item #300556039863].

Dave Manley [21030547] · Fri, 19 Aug 2011 09:29:46 -0700

I'd buy the Tek scope - that's a reasonable price, it they are very capable scopes - good vertical amps, good timebase, good triggering.

Ben Vehorn [21030757] · Fri, 19 Aug 2011 12:32:53 -0400

Hi Luca,

Yes, a palmtop one would be much more practical for me, I was just worried that I was asked to trace an 8mHz signal and it tops out at 1mHz.

I could probably justify the price of the Quad model if the extra features and bandwidth are worth it, would you say they are?

Ben Vehorn [21030757] · Fri, 19 Aug 2011 12:35:14 -0400

Ah shoot, I just posted that I'm leaning towards the palmtop model but the good thing about the Tektronix is that it's local so I could go pick it up immediately.

Luca Sasdelli [21010226] · Fri, 19 Aug 2011 18:48:51 +0200

Hi Ben,

if you think to trace the 8MHz signal, of course the 500kHz is unfit :) About the quad palmscope, I don't know anything about, except from some (good talking) reviews on the 'net, sorry about that.

The Tek is obviously the choice.

Leonardo Ascarrunz [no serial number] · Fri, 19 Aug 2011 11:02:06 -0600

Ben,

You should also consider getting a logic probe. This will be way more useful in troubleshooting digital logic signals.

Heinz Weierhorst [21010276] · Fri, 19 Aug 2011 19:47:41 +0200

Hi Ben.

I've took some time testing my Chroma with a scope and an audio cable and made some pictures from the signals. Most things "ouside" the scanning computer are audible. For the "inner" signals like !RD, ALE and !PSEN it needs a scope. Some other signals like !RDVEL, !RDNOTE and !KINT are hard to find even with a scope because they are single events. So lets go on and do some Audio test. On Z35 pin 2,15,7,10 and 14 there must be sound. These are the adresses for keyboard scanning and sent to stackswitches and their circiut. If one or more keys are hit a 8bit signal (KD0 to KD7) is sent to the scanning computer via a tristate busdriver Z34 by making the output enable(!E) low = !RD. So what is tristate? Each digital device has two logical states: High or low. A tristate device has third state: High impedance. So if if !E is high the LS244 is not in the circuit and does nothing! If no sound it could be a defective Z35 = 74LS175 or a missing !RD (scope).

Ben Vehorn [21030757] · Fri, 19 Aug 2011 13:57:19 -0400

Hi Heinz,

The only pin that makes any sound on Z35 is pin 8... there is a strong signal there but nothing on the other pins.

Heinz Weierhorst [21010276] · Fri, 19 Aug 2011 20:24:18 +0200

What? Z35 pin 8? Take a voltmeter and check if there is a voltage on pin 8. Negative probe to CR26 = 1N4001 cathode or white ring the posive to pin 8. This pin 8 is the ground connection for Z35 = 74LS175 and must be tied to digital ground.

Michael Grossman [21030350] · Fri, 19 Aug 2011 11:39:59 -0700

Ben, I have not followed the details of the thread but have you checked to see if any ICs feel hot? You might get lucky. On my chroma one of the LS244/245 type buffers had failed and was hot to the touch.

Just a thought.

Ben Vehorn [21030757] · Fri, 19 Aug 2011 15:05:55 -0400

What? Z35 pin 8? Take a voltmeter and check if there is a voltage on pin 8. Negative probe to CR26 = 1N4001 cathode or white ring the posive to pin 8. This pin 8 is the ground connection for Z35 = 74LS175 and must be tied to digital ground.

I strapped a voltmeter across pin 8 of Z35 and the end of CR26 that has the silver stripe and didn't read any voltage.

Ben Vehorn [21030757] · Fri, 19 Aug 2011 15:07:02 -0400

Ben, I have not followed the details of the thread but have you checked to see if any ICs feel hot? You might get lucky. On my chroma one of the LS244/245 type buffers had failed and was hot to the touch.

Hi Mike,

No, I hadn't checked that yet, thanks for the tip. I felt all the ICs on the keyboard-scanning end of the board and none were hot.

Bummer, that would have been and easy way to find out!

Ben Vehorn [21030757] · Fri, 19 Aug 2011 15:09:21 -0400

I strapped a voltmeter across pin 8 of Z35 and the end of CR26 that has the silver stripe and didn't read any voltage.

PS-- Yes, I just retested to make sure there was no user error. I get a strong audio signal coming off Z35 pin 8 but not on any of the other pins.

Ben Vehorn [21030757] · Fri, 19 Aug 2011 15:27:18 -0400

PPS-- another new development is that I can occasionally get the front panel to freeze up and the program number display to disappear if I mash a bunch of keys on the Chroma keyboard, forcing a reboot. External midi is still fine.

Heinz Weierhorst [21010276] · Fri, 19 Aug 2011 21:44:29 +0200

Hi Ben.

With an Ohmmeter or a beeper check if Z35 pin 8 is connected to digital ground. Go from CR 26 cathode to pin 8 direct not to the solder pad and after that to the solder pad. Normaly you should hear nothing 'cause the crocodile clamp is connected to ground and the hot end to ground too! In other words you have a short.

So if Z35 is not grounded properly it's "hanging in the air" and does nothing or wrong things.

Erik Vellinga [21010286] · Fri, 19 Aug 2011 21:47:25 +0200

Hi Ben,

I haven’t read the whole discussion yet but I wonder if your Chroma does SEND MIDI ? If not, do the benders send MIDI ? This is to obviously rule out your 8039. I know I’ve seen this before in my Chroma (ex, I sold it….) but can’t remember what the solution was.

In which part of the world do you live ?

Ben Vehorn [21030757] · Fri, 19 Aug 2011 16:50:07 -0400

With an Ohmmeter or a beeper check if Z35 pin 8 is connected to digital ground. Go from CR 26 cathode to pin 8 direct not to the solder pad and after that to the solder pad. Normaly you should hear nothing 'cause the crocodile clamp is connected to ground and the hot end to ground too! In other words you have a short.

Hi Heinz,

I'm not sure I understood this correctly so let's see if I did this right. I get continuity between Z35 pin 8 and the green back-panel ground connection . I also get continuity between CR26 leg and Z35p8 leg, and also between the 2 solder pads they are connected to. Is that what you meant?

Ben Vehorn [21030757] · Fri, 19 Aug 2011 17:01:14 -0400

I haven’t read the whole discussion yet but I wonder if your Chroma does SEND MIDI ? If not, do the benders send MIDI ? This is to obviously rule out your 8039. I know I’ve seen this before in my Chroma (ex, I sold it….) but can’t remember what the solution was.

Hi Erik,

The Chroma not sending midi, but is responding to it. The benders are working for the internal voices, I can play it via an external keyboard and use the Chroma levers properly. They don't send midi, though.

I bought some cheap spare 8039s and tried several but they did not fix the problem, unfortunately.

Ben Vehorn [21030757] · Fri, 19 Aug 2011 17:01:30 -0400

PS--- I'm in Akron, Ohio, USA.

Paul DeRocco [21030230] · Fri, 19 Aug 2011 21:42:03 -0400

Yes, a palmtop one would be much more practical for me, I was just worried that I was asked to trace an 8mHz signal and it tops out at 1mHz.

I could probably justify the price of the Quad model if the extra features and bandwidth are worth it, would you say they are? Thanks, Ben

1MHz is more than enough for audio, but if you use it to examine a strobe pulse in the Chroma, it will be heavily attenuated, just a little triangular spike. It's up to you, but if I were buying a scope for general use, I'd hold out for at least 50MHz.

Remember, you also need at least one 10X probe, preferably two, and make sure the input capacitance of the scope falls within the calibration range of the probe.

Paul DeRocco [21030230] · Fri, 19 Aug 2011 21:47:52 -0400

PS-- Yes, I just retested to make sure there was no user error. I get a strong audio signal coming off Z35 pin 8 but not on any of the other pins.

Relative to what? What are you grounding the audio cable to? You shouldn't hear anything on pin 8, because that's ground. You might hear a little digital noise if you're grounded far away. And you've already ohmed it out and found continuity to the rear panel.

Paul DeRocco [21030230] · Fri, 19 Aug 2011 21:55:14 -0400

That's right, but on the databus of the 8039 there is much faster "traffic". I don't believe it's the scanning computer itselfe but something outside. Because ALE is active the computer is doing a job but did he do right? May be the handshaking circuit isn't working proper and so on. The next information I need are the Pulses on KA lines active?

I suggested "listening" to the keyswitches, which should be pulsed at a kilohertz.

If the 8039 is getting 8MHz, then ALE will run, even if it's crashed. It's possible that the EPROM has one or more bad bits, causing the program to crash, in which case it'll execute some random loop over and over, without scanning the keyboard.

BTW. The note latch Z37 is 7 bit wide but only 6 bits are needed. Was there a plan to have a larger keyboard? Or is it so that 0 is an unwanted number? 0 to 63 or 1 to 64?

A larger keyboard was never more than an idle thought. And no, it uses 0 to 63.

Ben Vehorn [21030757] · Thu, 25 Aug 2011 10:50:22 -0400

Relative to what? What are you grounding the audio cable to? You shouldn't hear anything on pin 8, because that's ground. You might hear a little digital noise if you're grounded far away. And you've already ohmed it out and found continuity to the rear panel.

Hi Paul,

Just getting back to this after several days of letting it sit. I now have an oscilloscope (eBay item #300570165339, ARM DSO203 Nano V2/Quad Pocket 4CH Digital Oscilloscope) and am about to watch a tutorial on how to use it properly, so I now have that tool at my disposal.

I was grounded to the green ground strap on the rear panel. Z35 pin 8 is showing ground continuity, but it is also giving off an audio signal if I run it through an amp. Pin 1 is also giving off an audio signal, but none of the other pins on Z35 are.

Ben Vehorn [21030757] · Thu, 25 Aug 2011 10:53:21 -0400

I strapped a voltmeter across pin 8 of Z35 and the end of CR26 that has the silver stripe and didn't read any voltage.

Hi Heinz,

I now have an oscilloscope! I'm not sure where to go from here, I'll re-read the thread and see which tests you wanted me to perform that require the scope. If you have any suggestions for new tests to run, please let me know.

Ben Vehorn [21030757] · Thu, 25 Aug 2011 11:32:01 -0400

Just getting back to this after several days of letting it sit. I now have an oscilloscope (eBay item #300570165339, ARM DSO203 Nano V2/Quad Pocket 4CH Digital Oscilloscope) and am about to watch a tutorial on how to use it properly, so I now have that tool at my disposal.

I was grounded to the green ground strap on the rear panel. Z35 pin 8 is showing ground continuity, but it is also giving off an audio signal if I run it through an amp. Pin 1 is also giving off an audio signal, but none of the other pins on Z35 are.

Okay, disregard this last email from me. I'm going through and re-running all the tests and realized that somehow I was measuring the wrong IC *both* times (smacking self in head) and not Z35. Z35 pin 8 is grounded. I'm not getting any audio signal off the pins Heinz asked me to test, but they all show up as at least doing something on the scope, though some have very minimal activity.

Paul DeRocco [21030230] · Thu, 25 Aug 2011 10:10:08 -0700

Okay, disregard this last email from me. I'm going through and re-running all the tests and realized that somehow I was measuring the wrong IC *both* times (smacking self in head) and not Z35. Z35 pin 8 is grounded. I'm not getting any audio signal off the pins Heinz asked me to test, but they all show up as at least doing something on the scope, though some have very minimal activity.

You should see square waves on the outputs of Z35, that jitter when you play, with the slowest ones on pins 10 and 14 running at about a kilohertz, I believe. If you don't see this, then the keyboard scanner is not running. The two possible causes of this would be that the scanning CPU has crashed, or that the handshaking with the main CPU is broken and the scanner is stuck waiting for a response. In the latter case, I believe the scanner will work correctly until one, or maybe two, keys have been played. With a scope, it should be possible to rule this in or out in a minute.

If the scanner is crashed entirely, the most likely culprit, I believe, would be the EPROM, which after 30 years may have started dropping bits. If that's the case, reprogramming the EPROM, using data from another one, should work, because the dropped bits aren't a permanent failure of the part.

Heinz Weierhorst [21010276] · Thu, 25 Aug 2011 19:55:39 +0200

Hi Ben.

This weekend I will take some pictures from my scopes screen with two traces a time. What you should see is something like a 4 bit binary counter with some jitter. I did audio testing again and at pin 10, 7 and 15 you should hear a high frequency about 1.4Khz but with other harmonics and at pin 2 a low frequency. This was surprising me because pin 2 is the highest frequency pin 10 one octave lower and so on until pin 15 which is the lowest frequency. So if there is no sound, no keyboard scanning!

Ben Vehorn [21030757] · Thu, 25 Aug 2011 14:18:53 -0400

Hi Heinz,

My local electronics store had some 74s175 in stock so I went ahead and socketed/replaced Z35, so now I've replaced both Z35 and Z31. The behavior persists.

I checked the new Z35 with the scope and the only pin I seem to get a strong regular signal from is pin 12, the rest look like noise mixed with an occasional spike and/or ripple. So if it's not the keyscan CPU or Z35, would the keyscan eprom be the next likely culprit, as Paul suggests?

Ben Vehorn [21030757] · Thu, 25 Aug 2011 14:29:30 -0400

Hi Paul,

Yes, sadly no squares on the Z35, just a very narrow pulse with high amplitude coming from pin 12. I just retested since my last msg to Heinz and noticed these waves are jumping around a lot... jittery, not regular as I had stated.

Nothing changes when I play the keys, the waveforms stay the same.

Looks like the Z33 keyscan eprom could be bad? Would this be a good thing to replace next?

One thing that I noticed, though it looks factory/correct, is that the Z33 socket is 2 pin-widths wider (x2 rows for 4 unused sockets) than the IC itself, though the unused sockets don't seem connected to anything. Pin 1 of the IC is inserted in pin 1 of the socket so that, when facing from the front with the lid flipped up, the 4 unused sockets are all the way to the left and the IC is flush with the right of the socket. I'm assuming this is correct, can anyone confirm? It was working before and hasn't been moved so it should be right, but wanted to double-check.

Heinz Weierhorst [21010276] · Thu, 25 Aug 2011 21:13:10 +0200

Hi Ben.

The frequency at pin Z35 pin is about 2.7 Khz but no signals at pin 2, 10, 7 and 15? Try to check with your scope if on Z34 pin 1 and 19 three low going pulses are present. It's the !RD signal coming out on Pin 8 of Z31.

Next on Z33 pin 20. Are there low going Pulses? This signal is called !PSEN and coming out on pin 9 of Z31.

Check if pin 7 of Z31 is high.

And yes, the eprom is is a possible source for that error. I told you before that the eprom tells the scanning computer what he has to do.

Paul DeRocco [21030230] · Thu, 25 Aug 2011 12:54:54 -0700

Yes, sadly no squares on the Z35, just a very narrow pulse with high amplitude coming from pin 12. I just retested since my last msg to Heinz and noticed these waves are jumping around a lot... jittery, not regular as I had stated. Nothing changes when I play the keys, the waveforms stay the same. Looks like the Z33 keyscan eprom could be bad? Would this be a good thing to replace next?

Perhaps, but as I said, it's probably not that the chip is damaged, it's just that its data has started to leak away. If you can find someone who can program 2716 EPROMs, you can reprogram yours, with the data from the Rhodes Chroma web site.

One thing that I noticed, though it looks factory/correct, is that the Z33 socket is 2 pin-widths wider (x2 rows for 4 unused sockets) than the IC itself, though the unused sockets don't seem connected to anything.

Don't worry about that. That's just to allow the use of a larger capacity EPROM, which are in 28-pin parts. They made the pinout compatible by adding four lines to the end.

Ben Vehorn [21030757] · Fri, 26 Aug 2011 13:06:47 -0400

Hi Heinz,

I started testing these yesterday and then got lost in trying to figure out how to save the waveforms in the scope so I could take screen shots of the waveforms to show you.

I'm still having trouble figuring that out but get the feeling that the waveforms were not as expected.

In the meanwhile, David Clarke has kindly offered to burn me a new keyscan EPROM so replacing that will be the next step I take. Hopefully this will fix the problem! If not, I'm sure I'll have more questions... either way I'll report back once I've swapped it out.

iChromaCC+ iPad editor now supports wired connections

Michael R [21030869] · Sun, 14 Aug 2011 09:05:00 -0400

Hello group,

I pleased to announce that our iPad editor for the Chroma now supports wired connections, so you can directly connect it with a MIDI cable to your CC+ MIDI interface using the following iPad MIDI interfaces:

You will find more information on the FAQ page of our main website.

This means also that you can use iChromaCC+ in a computer-less workflow.

We have updated our main website and support website to help you choose an iControlMIDI qualified iPad CoreMIDI compliant MIDI interface or simply hook it up to your MIDI studio.

Ben Vehorn [21030757] · Sun, 14 Aug 2011 18:57:57 -0400

Hi Michael,

Is this bidirectional? If I have Ipad midi out-->Chroma and Chroma midi out-->Ipad in and load a patch, will the Ipad display update to the current Chroma parameters?

And it should work with any core-compliant midi interface (like the M-audio Uno), correct? I noticed you only listed a couple of specific devices but I'm assuming it should work with any compliant interface... please let me know if I'm wrong

Michael R [21030869] · Sun, 14 Aug 2011 21:21:12 -0400

Hi Ben,

Thanks for your interest in iControlMIDI / iChromaCC+

RE: Bi-drectional, no. Maybe in the future. It's one way iPad -> Chroma RE: CoreMIDI compliant interface other than the ones listed, in theory yes it should work, but I do not have a M-Audio Uno so I cannot guarantee it.

Ben Vehorn [21030757] · Mon, 15 Aug 2011 11:43:13 -0400

Hi Michael,

Thanks for the info. I'd like to put my vote in for bidirectional support as it seems like it would make a huge difference in being able to visualize and make slight tweaks to the parameters of a saved patch without making unintended major changes. On a simpler synth it's pretty easy to wrap your head around what's going on without having absolute knob value feedback but in the Chroma it's pretty easy to get lost due to the hugely flexible architecture.

A couple more questions:

  • If I purchase this and you later add the bidirectional support, would future updates be free?
  • I purchased your C4 template for the Chroma and found that the C4 didn't really fit my studio workflow so I sold it and bought an Ipad. Am I entitled to any sort of crossgrade or discount?

Thanks.

Michael R [21030869] · Mon, 15 Aug 2011 12:40:27 -0400

Hi Ben,

Please find answers to your questions:

  • If I purchase this and you later add the bidirectional support, would future updates be free?

Yes for existing customers, but if / when I add bidirectional support I might raise the App price.

  • I purchased your C4 template for the Chroma and found that the C4 didn't really fit my studio workflow so I sold it and bought an Ipad. Am I entitled to any sort of crossgrade or discount?

I'm open to that idea -thanks for purchasing the C4 Chroma template!-, please contact me off list michaelrosner underscore nyc at hotmail dot com

Power Supply on eBay

Chris Ryan [21030691] · Thu, 18 Aug 2011 17:36:36 -0700

Item #260837915915, USD$60.00. From the description: "This power supply needs a new solder in fuse."

Picture from the auction:

eBay260837915915.jpg

Paul DeRocco [21030230] · Thu, 18 Aug 2011 20:51:44 -0400

From the description: "This power supply needs a new solder in fuse."

Meaning it probably needs TWO fuses, plus that other thing you discover after you blow out the first replacement.

CEM3350

Doug Terrebonne [21030114] · Fri, 19 Aug 2011 18:34:46 -0700

Hi, how many people on the list be interested in CEM3350 VCF chips at $50ea? They are rather hard to find (I've never had any stock before). I still have a few CEM3360 as well ($55ea). Each Chroma voice board has 1 of each.

Luca Sasdelli [21010226] · Sat, 20 Aug 2011 03:54:26 +0200

Hi Doug,

I'm interested for 2-4 CEM3350s, depending on your stock and other listusers' requests.

Werner Schöenenberger [21010114] · Sat, 20 Aug 2011 09:30:45 +0200

Hi Doug,

thank you very much for the offer. I'm interested in two of them each, if available.

Frank McGing [21010198] · Sat, 20 Aug 2011 18:40:57 +0100

Hi Doug

Thanks for offering these! I would be interested in 2 x 3350 and 4 x 3360.

Go to next message in thread, September 2011

Any U.S. chroma techs out there?

RJ Krohn [21030455] · Sun, 21 Aug 2011 18:36:14 -0700

i've got 3 voice boards that do not pass tuning here, wondering if there are any techs in the states that would get them up to snuff, possibly? i'm not looking to ship my chroma, of course, just the boards. thanks, rj

Chris Ryan [21030691] · Sun, 21 Aug 2011 18:48:42 -0700

See Service Centres.

List Problems

Chris Ryan [21030691] · Wed, 24 Aug 2011 16:53:49 -0700

The list has been down for a couple of days, but should now be working. I know a few of you tried to send messages; please go ahead and try again.

chroma for sale

Keith Hedger [21030607] · Thu, 25 Aug 2011 10:26:20 -0400

I recently bought a Chroma on eBay [see Chroma with CC+ and Pressure Sensor Sold on eBay, July] but find I need to turn around and sell it. Some unexpected financial problems have reared their ugly heads. I'll include the original eBay description below. I haven't had a chance to do a lot with the Chroma, but everything seems to work fine on it.

I'm not really setup to ship it so this will have to be to 'local' buyers only - pickup in Cambridge, MA. I'm going to wait a few days before placing this on the local Craigslist. If anybody's interested, get back to me. I just need to break even on it... $4500.00 takes it.

the eBay ad [actually the posting from July]

"Rhodes Chroma with CC+ AND polyphonic aftertouch," item #130551360638, sold for USD$4,499.00. I've asked the seller for the serial number. From the description:

"Almost no units were shipped with the [pressure] sensor bar required. Fortunately, this one has Chris Borman's excellent kit installed, which takes the already impressive array of expression options to the next level.

"Of course, there was one more big drawback in the original Chroma that's fortunately solved here. When initially produced, it had no midi and frustrating single-slider dx-7-style programming. That's where the CC+ comes in.

"This Chroma was fully restored by the Good Guys in St. Paul, MN, who's reputation for fixing Chroma's is about as good as it gets. They still have guys with factory training that have been fixing these babies since they were new and work with many famous clients. The power supply was completely rebuilt and the synth functions perfectly. All voices tune up without fail. The cosmetic condition is very good , expecially for it's age. The tolex is in great shape with only a few minor scuffs and no tears and the wood is in great shape, though the surface finish has been warn down in places by foam rot (a notorious problem with the Chroma roadcase). It still looks good, and would look amazing with a little sanding and a few coats of finish. "

Go to next message in thread, September 2011

WTB: Chroma Enabler

Frank Hettlich [21030041+] · Thu, 25 Aug 2011 20:52:13 +0200

Hello list members,

finally got my 21030041 (with original ARP boards) updated by my tech to latest specs (newest firmware, polyphonic aftertouch and new SPSU) - hoorah!

I showed my tech all the common controller options (Behringer, Mackie, Enabler) and the new display option and we both came to the conclusion that there is only one "all wishes fulfilling" solution that addresses an ultra smooth "working" with the Chroma: the Chroma Enabler!

Before contacting Randel [21030467] I am asking IF someone would be willing to part with his? Chances are low, I know...

How are the experiences of those Chroma Enabler owners? Anything you still miss even with the Enabler?

All the best and good luck with the troubleshooting of Ben´s Chroma [see above] (sadly I cannot help as I am a dumb ass idiot when it comes to electronics)

David Clarke [21030085++] · Thu, 25 Aug 2011 22:35:36 -0400

... How are the experiences of those Chroma Enabler owners? Anything you still miss even with the Enabler?

I don't have an Enabler (and I'd ask those folks who have one to correct me if I'm wrong), but I think the one thing that may be missing to make it 'complete' is to have an indication of the actual parameter values currently in use.

For instance, if you select a patch on the Chroma and you like it - you won't know (for instance), what the filter cutoff value is in that patch. If you then use the enabler to adjust the cutoff value, then it will immediately jump to whatever value the enabler has commanded it to go to. While you'll now know what the 'new' value of the parameter is - you will have lost the original value that you only wanted to change a little bit.

That is actually one of the nice features of the BCR2000 as the rotary encoders, along with the 'data request' capability, allows you to see all of the settings before you make any changes (e.g., bi-directional parameter control) - and then when you make changes they're only incremental from the current settings (e.g., you don't have to 'jump' to a commanded value).

One possible optimal scenario would likely be something like the Enabler - but with encoders vs. potentiometers, and a live display of the currently selected parameter values.

A science experiment for someone might be disassemble a couple BCR2000's so that the encoders can be mounted on a panel like that for the Enabler - and then pair that up with the 4-line alphanumeric display from the CC+.

re-glueing the CPS etc.

Jesper Ödemark [21010135] · Sun, 28 Aug 2011 23:35:26 +0200

Hi list,

today I took my Chroma (21010135) out for surgery. The main goal was to install the CC+ 215 OS that a friend so kindly burnt for me on an eprom. But lately I'd noticed some clicking sound and uneven key responce I wanted to address too...

The prom change was quickly done. I haven't tested under midi yet, but I guess it'll be OK. It worked as standalone machine afterwards at least. :)

The key mess was due to those annoying cables dropping down on the keybed. That was easily fixed too. Good that the front panel has some additional holes along the inner bottom edge where you can tie the cables together...

The clicking proved a bit messier since it was the CPS PCB that had come loose from the wood spacer. I guess the heat of the interior of the Chroma isn't the best for the glue in pair with the pressure applied, maybe unevenly. Anyway, I wanted to mention my solution so that'll end up in the archives... A bit hesitant at using a glue gun direct on the PCB and with no other decent glue at home, I decided to glue along the edges of PCB/wood spacer and wood spacer/original Chroma damper. I settled on both places 'cause the loose board was so annoying that I don't want to redo it again in six months. While at it I added the extra washers under the damper mount and adjusted the CPS sensitivity.

Now the Chroma is fully responsive again, with good velocity action combined with fabulous aftertouch. A good stringspatch and I'm in Vangelis version of Heaven. This is such a wonderful instrument!

Dave Manley [21030547] · Mon, 29 Aug 2011 17:15:24 -0700

This thread makes me wonder what the factory method was for attaching a pressure sensor? Also, is there any reason not to not add some small wood screws?

(I have to admit to being guilty of not yet installing my CPS. Maybe this weekend...)

David Clarke [21030085++] · Mon, 29 Aug 2011 20:44:53 -0400

On 8/29/2011 8:15 PM, Dave Manley wrote:

This thread makes me wonder what the factory method was for attaching a pressure sensor? ...

The original had the circuit board/electronics attached to the damper bar with small "L" brackets and screws. That took all the weight of the assembly. Under the circuit board was just the (light) felt & rubber layers of the sensor, and that was glued - xref The Chroma Pressure Sensor & Interface, and specifically Figure 6 and Figure 7.

Chris Borman [21030194+] · Mon, 29 Aug 2011 20:55:03 -0400

Thanks Dave! Makes me not feel so bad about how long it took to make a kit available! Just install it! A couple snags so far. Nothing we can't work through.

Dave Manley [21030547] · Mon, 29 Aug 2011 18:01:45 -0700

Yeah, what can I say :-( too much work and not enough time for the important stuff! I did get the Chroma on the bench about a week ago and opened it up, trying to resolve a voice card issue. After revealing the degree of my procrastination to the list, I'll now have to get it done this weekend.

Chris Borman [21030194+] · Mon, 29 Aug 2011 21:14:41 -0400

The original had the circuit board/electronics attached to the damper bar with small "L" brackets and screws. That took all the weight of the assembly. Under the circuit board was just the (light) felt & rubber layers of the sensor, and that was glued - xref The Chroma Pressure Sensor & Interface, and specifically Figure 6 and Figure 7.

Given the fine Chroma kb, it has to mount upside down. My sci pro-one (mono) adaptation, or any Pratt kybd is gravitationaly correct, on the bottom, no where to be pushed off.

Dave Manley [21030547] · Tue, 30 Aug 2011 11:53:17 -0700

I looked at the CPS last night and the circuit board is separating from the wood strip like what Jesper is describing.

Before I install it, what's the recommendation to reglue it?

Jesper - what type of glue did you use?

Chris Borman [21030194+] · Tue, 30 Aug 2011 19:43:18 -0400

I don't know what Jesper used, but in light of the 3M 77 Spray adhesive failures, I am going to give Liquid Nails Home Project adhesive a try tomorrow. It is formulated to adhere wood to impervious surfaces such as plastic and fiberglass. I suspect the adhesive failure is occurring at the PCB FRP surface.

I will post my results tomorrow eve.

Andrew Dalebrook [21010180] · Wed, 31 Aug 2011 11:53:28 +1200

Could one perhaps score the PCB to give the glue a bit more hold?

Chris Borman [21030194+] · Tue, 30 Aug 2011 19:55:28 -0400

No.

Jesper Ödemark [21010135] · Wed, 31 Aug 2011 08:00:34 +0200

Dave Manley skrev 2011-08-30 20:53:

I looked at the CPS last night and the circuit board is separating from the wood strip like what Jesper is describing.

Before I install it, what's the recommendation to reglue it?

Jesper - what type of glue did you use?

First: I think Chris did a great job with the CPS. Even wonderful with such an easy drop-in replacement.

But after the transport from across the little pond known as the Atlantic I could already see signs of separation. When I did my re-glueing I first examined the PCB holes but they're all tiny and they all demand that you put a screw through the pressure sensitive strip and I didn't want to go there (remember, I had an extra wait 'cause my original CPS was malfunctioning and the replacement also had dropouts). It would also have meant that even with tiny screws the heads could build just fractions of a millimeter and change the action of one key. Not what I wanted either.

I used a standard glue gun. Cheapest possible version off the rack at your favourite home owners kindergarten for men. In the nordic countries the store is called Clas Ohlson. I bet other countries have their equivalents. (Conrad in Germany for example) :D

Here's a picture of what I mean.

Such glue dry extremely quick and even if you mess up, it can be scraped off with mechanical force. The most important for me (I keep thinking "for me" 'cause this is just my way of doing it) was to keep it off the PCB surface and away from the electronics.

I held the strips/lists/bars together and applied a string of glue along all four splices (the correct word?), two on each side. I didn't force any glue inbetween the parts. I only applied it on the edges and trusted in the stickyness of the glue. Piece of cake!

(With axtra washers/spacing below the bar assembly and the sensitivity pot at a maximum I love the action. I'm still to test it with the rest of the gear but now the Chroma is back in the studio at least, with master keyboard ambitions. :D )

I hope someone was helped by this...

Jesper Ödemark [21010135] · Wed, 31 Aug 2011 08:05:59 +0200

Chris Borman skrev 2011-08-31 01:43:

I suspect the adhesive failure is occurring at the PCB FRP surface.

Correct. Mine started coming away at the far right of the keybed. So it wasn't the weight of the MUX-board that was to blame even though mine isn't screwed to the damper bar. With the keys applying and releasing pressure as I played I guess it quickly spread along the PCB after that. The left part was still OK when I came rushing with my glue gun. :D

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