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ChromaTalk Archives: July 2011

supply voltage drop commuting across voices?

RJ Krohn [21030455]

hi all, i've got an interesting problem that im wondering if any you may have seen, or have insight into.

my chroma will regularly have one or two VB's fail tuning. but there's not a lot of consistency in WHICH voice. so i did some searching w/ a scope and DVM, and found that the board that fails, at least according to TP1 and TP2, has a voltage drop and inconsistent square wave. so, if a working VB will read about 3.01VDC and 4.56VDC at the test points, the failed board will read around 2.0 and 2.25, respectively. and the square wave will have the same amplitude, but it looks like its frequency is much lower (the screen will show a wider, and less many square waves-sorry for the laymans lexicon).

and that problem can commute from one board to another; i can have voice 0 fail, and behave in this manner, turn off/leave for an hour/come back, and voice 0 will work AND show "proper" specs at test points, but voice 3 will now fail and show improper specs.

im assuming that something on the motherboard that is feeding the voice boards voltage has an problem; does that seem like a fair guess? any specific ideas which? i've checked the I/O board calibration, and its showing 0.0V so im assuming its not that. thanks, rj

Heinz Weierhorst [21010276]

Hi RJ.

Don't care about the DC-level on TP1 and TP2.

If a voice fails autotuning the oscillators are set to a low frequency appr. 10-11Hz. It doesn't matter if it is a wrong OSC, FLT or AMP on a DVB. That voice is "killed" by software.

Try SETSPLIT 31 and check out each voice.

Another thought is that the 1uF caps on the filter amp have dried out. Replace them with good quality electrolytic or with WIMA MKS-02 1/10 inch contact spacing foil caps as I did - thanks to Paul DeRocco [21030230].

The MOLEX connectors on the DVBs are a critical point too. I will start a test and clean the contacts with DEOXITE D5 from CAIG Laboratories.

Luca Sasdelli [21010226]

I agree with Heinz; about the connectors, in some cases I had unexpected improvements by re-solder them clean. Indeed they're a fault point IMHO.

Does anybody know their Digi-Key part number or similar?

RJ Krohn [21030455]

oh! thanks. so it is possible that the faults are local to the voice boards, and that when the autotune function kills the voice, it causes the waveshape at TP1 and TP2 to go wonky? hmmm. ok. maybe i should replace all the elec caps on the VB's....

David Clarke [21030085++]

...Does anybody know their Digi-Key part number or similar?

For the voice-board side, check out Happy new year! motherboard, and VB harness questions [January].

In summary, P/N WM2817-ND and WM3006-ND both seem fine.

Luca Sasdelli [21010226]

Excellent, thanks!

Chris Ryan [21030691]

Item #290583178397, starting bid USD$0.99, no bids yet, ends July 11. Not completely clear what this is; the description says "Your bidding here of casetten data 2 factory patches 50+50 best work-sounds for rhodes chroma analog synthesizer! Maby in mp3 format or data-casette!" The seller is also looking for an "Atari 1040 bankloader (omnibänker, kirschning, cubase-satelite etc. Or other bankloader)."

Data Sounds on eBay

Chris Ryan [21030691]

Item #290583178397, starting bid USD$0.99, no bids yet, ends July 11. Not completely clear what this is; the description says "Your bidding here of casetten data 2 factory patches 50+50 best work-sounds for rhodes chroma analog synthesizer! Maby in mp3 format or data-casette!" The seller is also looking for an "Atari 1040 bankloader (omnibänker, kirschning, cubase-satelite etc. Or other bankloader)."

See eBay updates below.

Reminder to Check your Chroma Batteries

David Clarke [21030085++]

Today I turned on a Chroma that I hadn't had run for a while - and lo and behold, the keyboard didn't start up.

I don't have a CC+ in all of my Chroma/Expanders - and sure enough this one still had batteries in it, and they died, causing a leak.

The damage was luckily minor - but it could have been much worse.

If you haven't done so in a while, this is a reminder to check the condition of the batteries in your Chroma.

Issue a "Set Split-6" ("Special Funct-6" on your Expander) and view the voltage in the display window.

If the displayed value is notably under 3V, it would be good to check/replace the battery (the Service Manual says anything under 2.5V is bad).

(Batteries are cheap - CPU boards aren't. A set of fresh batteries is a nice preventative measure.)

P.S. If you've already had battery problems, and want to replace the battery holder, a match to the original is Keystone part number 2140: Keystone Battery Holders (PDF).

The coloured plastic cups are also available: Digi-Key - 59K-ND (Manufacturer - 59).

P.P.S. if you wanted to check your Polaris at the same time - that would be LF-D-1. Two or more LEDs in the assignable Control section indicates things are OK.)

Luca Sasdelli [21010226]

A "classic" Chroma failure, indeed :)

On my previous CPU board, just sold on eBay, I replaced the battery holder with a 3.6V NiCD rechargeable battery; the charge is done from the +5V bus via a 180 ohm resistor in series to a 1N4007 diode, so the charging voltage is 4.3V and the current via the resistor is sufficient to keep the battery in charge without stressing it. SetSplit-6 shown voltage was around 3.30V.

Doug Terrebonne [21030114]

A NiCad on a CPU board? Not the best idea (see Korg Polysix)...

Jesper Ödemark [21010135]

I recently saved a Siel Opera 6 and a Simmons MTM. It's a very good idea to get the batteries far away from the original location. Preferably in a location where leakage cannot harm the electronics. But do check those recharging circuits...

Heinz Weierhorst [21010276]

Hi Jesper.

When I bought my Chroma the batteries were placed via two long wires beside the highest key. A good idea indeed. But it would be better to use a sealed box.

Jesper Ödemark [21010135]

Sounds like a good idea but yes, a sealed box is even better. The Polysix way is the worst - that's been proven by history. :)

New EQ Board

Chris Ryan [21030691]

Heinz Weierhorst [21010276] has contributed an article on building a new EQ board, including schematics and PCB. Thanks, Heinz!

Daniel Rickenbach [21010172]

Hi

this looks very fine and I'm thinking about to build a new EQ board (because mine has a acid damage). Unfortunately, analog devices has discontinued SMM2164. But there is possible replacement with THAT 2162.

THAT Alternatives to the Analog Devices SSM2164

Heinz Weierhorst [21010276]

Hi Daniel.

I'm sure there will be a lot of SSM2164 around the world. Behringer used them in mixers and so on. But the price will get higher and higher. So it's good to know that the THAT 2162 is a replacement. THAT CORP. has a very good balanced driver too for replacing the DRV 134. It's a pin to pin replacement. The only trouble is that components are not easy to find in europe.

Power Supply on eBay

Chris Ryan [21030691]

Item #300574770011, starting bid USD$250.00, no bids yet, "buy it now" for USD$440.00. "Used but last [known] to be in working condition."

Picture from the auction:

Luca Sasdelli [21010226]

Uhm... besides from the pricing, it includes the back panel with jacks etc., i.e. it comes from a dismountled Chroma. So, why take apart a Chroma in "working condition"? :)

Moreover: "New other"; "A new, unused item with absolutely no signs of wear".

Simply a thought.

Re: Expander on eBay

Go to first message in thread, April 2011

Chris Ryan [21030691]

This finally sold after being relisted yet again as item #180659193646, for USD$6,800.00, apparently back in May.

Jack Colburne [21030142+]

$6800

I have no other words...

:P

Paul DeRocco [21030230]

I hope they were Zimbabwean dollars.

Chris Ryan [21030691]

The original list price was USD$3,150.00, so this is more than double what a new one cost all those years ago. 16310021 apparently sold for AUD $9,150.00 last year—though Matt doubted it, for some reason.

Eric W. Mattei [21030443+]

I wish I was willing to sell my Expander [16330105]. I could use the money! But I couldn't do that. The Chroma would get lonely.

Chroma and EQ Board on eBay

Chris Ryan [21030691]

The Chroma is item #200628733675, ends July 19, one bid of USD$3,000 but the reserve price is not met. I've asked the seller for the serial number.

From the description: "This vintage Rhodes Chroma has been fully and meticulously restored by The Analgo Lab/Expert Audio Repair Service in New York City. Analog synth guru Jeff Blenkinsopp built a completely new power supply which is much more stable and reliable than the original one. (The original one failed, as they notoriously do.) The tuning is ultra stable on the instrument now ... for a complete description of what was done to the power supply, [see SPSU Kit]. They also shot a nice video that demos the synth and shows it looks great, is fully operational and sounds awesome!

"I have already spent more than $1,500 worth of repairs and rebuilding of this instrument, so it is not the typical ebay restoration project- that has already been done and it is ready to play! A faulty voice was repaired, so that all voices register and autotune properly, the keys have been re-aligned and contacts cleaned, etc. The original factory pre-set sounds have even been loaded in! In fact the Analog Lab is offering a 30 day guarantee on all parts and labor on the work they've done- that 's how confident they are- I've had them do all my repairs for years and can tell you from experience they are first rate and do things properly- Jeff B. was the head tech for Pink Floyd for many years and has a degree in electrical engineering.

"The instrument also comes with the original owners manuals and service manual, complete with schematics, and a fully functional J. L. Cooper Chromaface , which is a MIDI interface box made for the Chroma by JL Cooper. The MIDI works beautifully, as you can see in the video.

"The only thing not covered under the guarantee is the keys going out of alignment, as this can happen slightly in shipping, but is not big deal to re-adjust. Not only does everything work 100%, but it is in good shape cosmetically, with only some discoloration on the side wood panels- and these could be refinished if you want to get it looking absolutely mint."

The EQ Board is item #300576008855, ends July 12 (tomorrow), one bid of USD$35.00. This is from Syntronics, which has been parting out a Chroma for a couple of years. John Koumoutseas wrote a couple of years ago, when I asked him about a footswitch for sale at the time, "I have some other parts and a whole unit but missing 2 osc. bds. It works as a unit but the kybd contacks are hardto clean. I trying to decide if it is better to part it out. ... It's serial # is 0008 [I don't seem to have received an answer about which model, so didn't put it in the registry] but I'm not sure if it's just the board it's on and not the full unit. I have 2 lids, one is blank and the other has the big RHODES logo on it, I also have some Ic's."

In terms of further information for this part, all that's said is "last known to be working."

Chris Ryan [21030691]

The EQ Board is item #300576008855, ends July 12 (tomorrow), one bid of USD$35.00. […]

Sold for USD$41.11.

Chris Ryan [21030691]

The Chroma is item #200628733675, ends July 19, one bid of USD$3,000 but the reserve price is not met. I've asked the seller for the serial number. [...]

This is Chroma 21030526, which has changed hands a couple of times over the years.

Nobuya Tanaka [21030272]

serial # 0008 Chroma

The EQ Board is item #300576008855, ends July 12 (tomorrow), one bid of USD$35.00. This is from Syntronics, which has been parting out a Chroma for a couple of years. John Koumoutseas wrote a couple of years ago, when I asked him about a footswitch for sale at the time, "I have some other parts and a whole unit but missing 2 osc. bds. It works as a unit but the kybd contacks are hardto clean. I trying to decide if it is better to part it out. ... It's serial # is 0008 [I don't seem to have received an answer about which model, so didn't put it in the registry] but I'm not sure if it's just the board it's on and not the full unit. I have 2 lids, one is blank and the other has the big RHODES logo on it, I also have some Ic's."

That's my 0008 ARP Chroma with Arp logo. I've known from Chris's post that John Koumoutseas sells my ARP Chroma as parts

This is a really sad story. 15 years ago, I was a Berklee College of Music student, then I asked John to repair my 0008 ARP Chroma. I remember I paid $800 around.

After his repair, the keys were really bumpy. So I asked to repair again. But he didn't fix my chroma until I leave from Boston. As a result of that, I lost my chroma and even him. He had a synth repair shop in 466 Commonwealth Ave. Boston those days. If John said that It's serial # is 0008, that's absolutely mine.

That's the reason why John can't reply to Chris's question exactly. As you guys know well, the first fifty is ARP Chroma, not Rhodes Chroma.

I own Rhodes Chroma 21030272 and Expander 16330138 now. The Expander with KMX MIDI converter is from G&L Musical Instruments Steve Grom [21030502+] in 2010

Nobuya Tanaka, Tokyo Japan (No Radiation)

Chris Ryan [21030691]

Re: serial # 0008 Chroma

I've asked John about this. Seems to be a day for controversies.

I've added 0008 to the registry under Miscellaneous; I assume there was no model number, or at least it's unknown at this point. Also added 21030272 and updated 16330138. Do you have any pictures or other information for these instruments?

Good to hear you're radiation free.

Chris Ryan [21030691]

Sold for USD$4,500.00.

eBay Updates

Chris Ryan [21030691]

On 17/06/2011, at 9:48 PM, Chris Ryan wrote:

Item #200620070081, starting bid USD$0.99 and no bids yet (reserve not met), ends June 21. Description: "These are Genuine Rhodes Chroma Service manual (full schematics) and Programming manuals. I have had these kicking around on a shelf for years and here they are for anyone that wants or needs them." Service Manual looks original, while the Programming Manual appears to be a photocopy.

Sold for USD$75.00.

On 01/07/2011, at 1:49 PM, Chris Ryan wrote:

Item #290583178397, starting bid USD$0.99, no bids yet, ends July 11. Not completely clear what this is; the description says "Your bidding here of casetten data 2 factory patches 50+50 best work-sounds for rhodes chroma analog synthesizer! Maby in mp3 format or data-casette!" The seller is also looking for an "Atari 1040 bankloader (omnibänker, kirschning, cubase-satelite etc. Or other bankloader)."

Sold for USD$0.99.

Chroma 21030401 For Sale on Boston Craigslist

A number of "bad trader" posts were made in this thread regarding the person variously known as A P Chowdhury, Adam Chowdhury, Pierre Chowdhury, A P Yurow, Uro, A P Yurovski, Pierre Yurovski, and Yurovski. These posts have been removed only in order to avoid provocation. As with any transaction originating online, be careful and make sure you're covered.

Chris Ryan [21030691]

Posting ID 2492945918. "In excellent condition. Everything on the unit is fully functional. I am an engineer and I refurbish vintage synths for a living. This particular unit has also had a new power supply installed in the unit. The new supply is superior to the old one in every way, and weight 6 pounds less than the old one. You won't find a unit like this that is free of issues very often."

21030401 was previously reported as damaged beyond repair, but is in "near mint condition," according to the seller.

Bruce Sklar [21030660]

Is this David White- Analog Keys??? I was not at all happy with his very expensive work. (CC+ FIXED EVERYTHiNG.) I MADE A 1300.00 $ mistake taking my chroma there

Chris Ryan [21030691]

It's New England Analog.

Chris Ryan [21030691]

This is now listed as eBay item #260818003048, "Mint Rhodes Chroma Fully Restored," USD$5,000.00, ends July 21. "The unit has been fully restored and has had a new, modern power supply upgrade added as well. This new power supply runs incredibly clean and weighs much less than the old one did. Every function in the unit works 100%. The unit comes with a road case as well."

Chroma 21030828 on eBay

Chris Ryan [21030691]

Item #260822534712, starting bid USD$3,995.00 with no bids yet; or price of USD$4,550.00; ends August 1.

From the description:

"I'm the single original owner of this amazing Vintage Rhodes Chroma. This refurbished Chroma works as flawlessly as it did on the day I bought it. It has a new, completely upgraded, power supply. All voices register and autotune properly. The original factory pre-set sounds have been loaded from the original cassette that comes with the keyboard as does the original Anvil Flight Case. You won't find a better Chroma than this one.

"This beloved, historically significant keyboard has been carefully upgraded in 1986 at the CBS Fender Rhodes factory where they replaced the power supply and new eproms, and again in 2009 by Steve 'Doc' Hickerson, a factory authorized Chroma technician who put in a brand new, completely redesigned power supply and brought the keyboard to like new spec. Doc has worked on Chroma's since they were introduced. He has a reputation for experienced, knowledgable, excellent work and has been trusted by a list of famous performers, to include Eric Clapton.

"This is my 2nd Chroma. I purchased the first in June of 1983 at Music Sound World in Tulsa, Oklahoma […] In 1984 CBS/Fender sent me a brand new (improved edition) Chroma, with the latest version of their upgrades and fixes. This is the one is the one being sold here.

"As is common with the ATA flight cases that came with the keyboard, the inner lining decomposed, staining the wood side boards. I cleaned it up in 2009 when it was refurbished (see pictures [21030828]).

"This Chroma is fully operational and as ready to use as it was the day I bought it. A copy of the manual is included (they never gave me an original… just a copy!). The original cassette tape of voices from the factory is also included."

Go to next message in thread, September 2011

Introduction

Andrew Howson [21030209]

Hello fellow Chroma users,

I won an eBay auction for a Rhodes Chroma last month, although was unable to get my hands on it until today as it was stored with family. I understand the list likes to keep track of existing Chromas, so I'll include a little information here. It's got a PSU upgrade, which looks like a MKIII PCB of some sort and a switching power supply, and the CC+ upgrade. The serial number looks like it was just written by hand on the inside, as I couldn't see it printed on a PCB or what-not elsewhere, and it is [21030209]. I paid $2,500 CAD, which I think was a pretty good deal! It seems to be working well, and it sounds great! Attached below is the eBay auction link.

Item #150619507937. Here's the picture from the auction:

Although I'll have to get my finances in order first (I also recently had a child), I'm interested in acquiring a poly keyboard pressure kit and replacement parts should problems arise. Of particular interest is the CEM3350, as I understand it can be difficult to source, although hopefully a clone or suitable replacement will be made available at some point in the future. I welcome e-mails directly or through the list in regards to these interests. I would also welcome any e-mails regarding the alphanumeric display, as I'll certainly be having to figure that out soon. Any other advice for a newcomer is welcomed as well :)

I have a question regarding the limited steps of resonance on the filter. Would it be possible to cut the trace from the digital controller, and connect it to a makeshift PCB with a pot sending a smooth, continuous control voltage to the filter path? I presume the limited steps of resonance is a product of the interface, and not of the filter chips themselves.

Jesper Ödemark [21010135]

[...] understand the list likes to keep track of existing Chromas, so I'll [...] it is [21030209]. I paid $2,500 CAD, which I think was a pretty good deal!

Congrat's! Early in the production run [Andrew's initial post indicated the serial number as 2103029, which Jesper interpreted as 21030029; it's actually 21030209] and a very decent price with those upgrades.

I have a question regarding the limited steps of resonance on the filter. Would it be possible to cut the trace from the digital controller, and connect it to a makeshift PCB with a pot sending a smooth, continuous control voltage to the filter path? I presume the limited steps of resonance is a product of the interface, and not of the filter chips themselves.

Good question. But you'd loose the programmability. It might be worth it though...

Luca Sasdelli [21010226]

Il 23/07/2011 11:19, jesper ha scritto:

smooth, continuous control voltage to the filter path? I presume the limited steps of resonance is a product of the interface, and not of the filter chips themselves.

You're right: the resonance is a three-bits resolution stuff; a list member (maybe Heinz?) already sent an idea to use 4 bits for resonance, thus bringing its resolution from 8 to 16 steps. This would include a firmware mod anyway.

The "MkIII" PSU is the latest one :)

Heinz Weierhorst [21010276]

Hi Luca.

Increasing the Q-control by an additional bit and a 113 K resistor will give only 15 steps if the circuit remains unchanged. The saturated Transistors ( Q8, Q9 ) will not conduct because the current flowing trough that 113 K resistor is to low when the 3 other resistors ( 13 K, 27 K, 56 K ) are tied to ground.

In Chroma reading this would be: 0-13 variable Q, 14-15 oscillation.

On the other hand it's a lot of programming, a new Eprom on CC+ and additional hardware on the DVBs.

Andrew Howson [21030209]

Update / Problems

Hello fellow Chroma users,

Just an update here regarding my recently purchased Rhodes Chroma.

As I had clarified with Chris off-list, having missed a digit in my previous message, the serial number is 21030209.

Furthermore my Rhodes Chroma isn't making any sound! It had made sound initially, when I tested it shortly after purchase, but after being transported to my home it no longer makes sound of any kind. The buttons respond, and when I move the volume slider I can hear that "scratchy pot" sound very faintly. I've read in the archives of a similar problem may involve a blown ADC/DAC. Z24.

In addition to this, one of the voice cards isn't working. To my frustration the original seller, Kerry Bonn, likely knew this when he sold it to me. I had stated, when testing it in his presence, that on start-up the display reads "Err 0", which I interpreted to mean there are zero errors -- an interpretation I expressed verbally. After researching the previously mentioned issue I discovered one of the voice cards is in fact referred to as voice card "0", so one of the voice cards was being disabled from the onset. A look back on the history of this serial number indicates the seller had previously reported one of the voice cards as dead.

In all likelihood I'll have to get the problem of no sound fixed by a local tech, as I can't imagine shipping the bulk of the Chroma anywhere. Having the dead voice card fixed should be a little easier, as I can pull it and mail it to someone with experience. I would appreciate any assistance, suggestions, and help, particularly in advising who would be an ideal candidate to fix the dead voice card.

Werner Schöenenberger [21010114]

Re: Update / Problems

Hi Andrew,

A question first: Does the synth still show "Err 0" after powering up? If yes, then at the moment, I would think of two things:

  • in the EQ-Board, the 3360 or some of the 4558 opAmps are dead, or might have a soldering issue. I just fixed an EQ board that did not sound by re-soldering the 3360. The effect was that when BASS Eq was at highest position, no sound could be heard. When having BASS Eq in lowest position, sound can be heard.
  • there might be an issue on the Channel Mother Board. I once had a Chroma where a component on this board was faulty (if I remember correctly, it was the output mute latch) and therefore nothing worked.

If the synth does not show "Err 0" at power up anymore, I would suggest to investigate the data latches on the channel mother board.

So this would be the parts to search first.

NB: I do not like people who know about errors in the items they sell and do not tell about these...

Good luck

Andrew Howson [21030209]

Re: Update / Problems

Thanks for the quick reply Werner.

Yes, the "Err 0" code still displays upon boot-up. I'll trying adjusting the EQ accordingly, and report back.

Leonardo Ascarrunz [no serial number]

Re: Update / Problems

Move the bad voice card to a different slot. If the error moves with the card, then its the card itself that is the problem. Also try a complete computer reboot after you have switched on the power , sometimes the first voice card fails tuning due to power supply instabilities when the chroma first boots up. Set split 50 i think is the reset command.

David Clarke [21030085++]

Re: Update / Problems

... Furthermore my Rhodes Chroma isn't making any sound! It had made sound initially, when I tested it shortly after purchase, but after being transported to my home it no longer makes sound of any kind...

As noted by others, the Err0 does indicate that voice board 0 is failing tuning. This could be due to a sick voice board, but it could be as simple as a voice board out of adjustment, or a power supply setting just a little too far adjusted one way.

As noted by others, the first step will be to find out if the issue follows the card or the card location.

With regard to the 'no output', there are some non-fatal potential causes of this, so those would be good to rule out first.

First, if there are any pedals attached (esp. a volume pedal), I'd recommend removing them. I'd also recommend removing all other back-panel 1/4" or XLR connections.

When any pedals removed, power up the Chroma. It had previously been noted that the unit had a CC+ installed, so we'll want to go into the programming interface for that (by pressing [Set Split][36]).

When in there, select parameter 17. This is the setting for Local On/Local Off. You'll want to make sure that's set to "On", otherwise the keyboard data won't allow parameters to sound.

Now select parameter 22. This should be set to "Chro" vs. "Pndr" (to configure the CC+ for the Chroma, vs. the Chroma Expander) - since if Pndr is chosen, keyboard input will be ignored.

Exit programming mode with [Set Split][36].

To ensure the lack of sound isn't due to something odd in the Patch/patches, start with a scratch patch. The quickest way to get one of those is to select [Set Split][39]. You should see a "0" in the big 2-digit LED display.

With this setup, I'd check to see if you have any output on any of the 1/4" audio outputs.

If there's no audio at all, I'd check inside to see if any cables perhaps came off - especially if this issue only seemed to come up after moving the unit.

You can also turn on 'voice watch' mode ([Set Split][37]). If you don't see items show up in the small LED display when you press the keys, they it would seem that the Chroma isn't seeing your key-presses (perhaps due to the connector for the keyboard data being disconnected).

Good luck, and let us know how you make out.

Luca Sasdelli [21010226]

Re: Update / Problems

In addition to the mentioned hints, give a [SetSplit] [1] to be sure that the output path is correctly selected.

Andrew Howson [21030209]

Another Update / Problems

Hello everybody,

First of all I want to thank everyone for their assistance. It feels bad enough getting burned in a deal, and I'm sure we've all been there before, but the abundance of detailed support you've offered me has certainly made the situation easier.

I swapped voice card 0 with voice card 3. Upon boot-up I got an error stating "Err 3". I will have to pull this voice card, and send it someone for service. I would appreciate suggestions. Obviously if I am going to mail it to a tech for repair I would prefer that they don't require me to send the Chroma as a whole, either because they have a unit to test it with or because they've got enough experience with these voice cards to work on them separately. I will likely have a local tech work on the audio output problem anyhow, so perhaps I'll see how they feel about working on the voice card as well. In such a case I will refer them to RhodesChroma.com and the e-mails I have received in regards to these specific problems.

I have tried altering the EQ, to no effect. I have ensured at boot-up there are no inputs or outputs being used, save for the power input connector. I have checked and rechecked cables and connectors, and it does not appear as though anything has come loose, and I've gone so far as to remove and replace what appears to be the cable connector to the board next to the CC+ board to ensure a good connection. Grounds wires appear to still be in place. I've altered parameters in Set Split 1, and listened on each audio output, to no avail. I've entered in to Set Split 36, found in parameter 17 the local is turned on, and found in parameter 22 the setting is for "Chro". In set split 39 "0" appears in the large display, and none of the audio outputs seem to work. In Set Split 37 there are no characters displaying on either display when keys are being pressed.

There are however some oddities.

The first is that sometimes, although not often, when I've entered in to Set Split 36, once I've gone in to parameter 17 or sometimes parameter 22, the lower keys are responsive. The upper and middle keys do not respond. When the lower keys produce sound they do not necessarily correspond with the keys being pressed, and they change randomly when no keys are being pressed. Sound will continue being made until I've entered in to a new parameter. When sound is being produced in this manner characters on both the large and small displays flicker, although they do not appear to change.

The second oddity is that on powering-up the Rhodes Chroma sometimes, although not often, only an "E" appears on the smaller display to the left. Even more infrequently the Chroma will appear to have powered up normally, with "Err 3" in the small display and "EP" in the large display, and then the large display quickly turns blank and only a "3" appears in the right of the small display. In either case the interface for the Rhodes Chroma appears to be disabled, and nothing can be done aside from powering down the unit.

In addition to these oddities, Set Split 31 yields "PL. 5" on the small display. Set Split 32 yields an "Err 0367" on the small display. Set Split 33 yields "PL. 5" on the small display. Set Split 50 yields "Err 3" on the small display, just as if I had turned on the Chroma. If anyone can shed some light on the different results between Set Split 32 and Set Split 50 I would appreciate it. I understand Set Split 31 and Set Split 33 do not disable defective voice boards, so it does not surprise me to find they yield "PL. 5" on the small display.

It appears at this time I will need to seek the assistance of a tech, but as I previously alluded to I'll probably have to wait about a month before I can afford to do so. Despite all of this I am committed to getting this Rhodes Chroma back on track, and using it as one of the polyphonic centerpieces of my setup. If anyone has anymore suggestions or advice that may help me test these issues further, or help a tech track down the nature of the problem(s), I would appreciate it.

Leonardo Ascarrunz [no serial number]

Re: Another Update / Problems

If you are at all proficient with a soldering iron you could try replacing the analog multiplexers in the faulty voice card. The cost about 2 dollars each and would take about 15 minutes. Usually this is the first chip to fail. If that doesn't work you would need an oscilloscope to continue the troubleshooting.

Luca Sasdelli [21010226]

Hi Andrew,

just a small suggestion, that happened to me recently when working on a faulty Chroma: below the Channel Motherboard there is a green earth cable, that in my very unique case was punched by a component stud, thus earthing a data bus line, so making the whole instrument mute and making very strange behaviours from CPU. To check it is enough to remove all DVBs and unscrew the CMB from base.

I'm generally convinced that the more complex is the symptom, the more stupid is the cause :) BTW: once removed the CMB, I suggest to replace its filtering electrolytic capacitors near the wire connections.

Just my 2 cents

Paul DeRocco [21030230]

From: Leonardo Ascarrunz

If you are at all proficient with a soldering iron you could try replacing the analog multiplexers in the faulty voice card. The cost about 2 dollars each and would take about 15 minutes. Usually this is the first chip to fail. If that doesnt work you would need an oscilloscope to continue the troubleshooting.

My experience with my two instruments is that the most common failure was C13 and C14. When they dry out they prevent the filter from self-oscillating, which is one of the steps in the auto-tune process. They're even easier to change.

Heinz Weierhorst [21010276]

Re: Another Update / Problems

Hi Paul.

Yes you're right. I've repaired a DVB from a Chroma user in Germany yesterday which did not pass autotune. With Setsplit 31 that board seems to work.

So I replaced that caps with Wima MKS-02 1uF foilcaps with 1/10 inch contact spacing because I don't like electrolytics in the audio path. See also WIMA - Competence in Capacitors .

That German user told me that his Chroma has had trouble with the ribbon cable from the I/O board to the DVB.

Heinz Weierhorst [21010276]

Re: Another Update / Problems

Hi Paul.

I have to correct: It should read the ribbon cable from I/O board to CMB.

Chris Ryan [21030691]

Re: Another Update / Problems

On 24/07/2011, at 9:20 PM, Future_Sound _Of_Canada wrote:

I swapped voice card 0 with voice card 3. Upon boot-up I got an error stating "Err 3". I will have to pull this voice card, and send it someone for service. I would appreciate suggestions.

The closest is probably John Leimseider [21030434++] at Cantos in Calgary (direct link).

David Clarke [21030085++]

Re: Another Update / Problems

... In Set Split 37 there are no characters displaying on either display when keys are being pressed.

This may partially explain why no output is heard.

The Set Split 37 configuration should result in a visual indication in the small display any time a key is pressed (assuming the keyboard parameters are OK).

If nothing shows up, esp. with a scratch patch, then something funny is going on and it wouldn't just seem to be an analog audio issue.

... The first is that sometimes, although not often, when I've entered in to Set Split 36, once I've gone in to parameter 17 or sometimes parameter 22, the lower keys are responsive. ...

There shouldn't be anything preferential about the upper or lower keys - aside from maybe if there was a 'split' set in the stored program.

Going in/coming out of the programming mode (set split 36) will cause a 'restore' of the channel parameters - and so that can partially explain why some 'different' behaviour might result - but it doesn't explain the overall behaviour about sounding notes.

... The upper and middle keys do not respond. When the lower keys prooduce sound they do not necessarily correspond with the keys being pressed...The second oddity is that on powering-up the Rhodes Chroma sometimes, although not often, only an "E" appears on the smaller display to the left. Even more infrequently the Chroma will appear to have powered up normally, with "Err 3" in the small display and "EP" in the large display, and then the large display quickly turns blank and only a "3" appears in the right of the small display...

If the chroma had an original CPU board, with battery damage, then that would be my initial suspected cause for such odd behaviour.

... In addition to these oddities, Set Split 31 yields "PL. 5" on the small display. Set Split 32 yields an "Err 0367" on the small display. Set Split 33 yields "PL. 5" on the small display.

I'm not aware of any intentional operation that would result in a "PL." in the display.

When you initially press "Set Split", you should see "SPL" in the left hand part of the display, with a positive or negative number on the right-hand side of the display (indicating the keyboard split point).

If it comes to it, I can provide a 'ram test' EPROM image to run on the CC+, just to help ensure that the CPU board's memory is OK.

Bad behaviour in Set Split 32 and 33 shouldn't be worried about. Those modes exist to support running the code via an emulator - and so running those even on a 'good' Chroma will result in boards being marked as failed.

... It appears at this time I will need to seek the assistance of a tech...

The good news is - the service manual is free, isn't a bad resource and the design is such so that debugging isn't bad. There's also very few truly unique parts - and so these units are very serviceable.

Andrew Howson [21030209]

Re: Another Update / Problems

Hello everybody,

Thank you very much for all of your assistance. As I am not proficient with a soldering iron I'll hopefully be having a local tech check out my Rhodes Chroma later this week. I may not get it fixed immediately, in order to keep costs manageable at the moment, but I'll keep the list updated with the tech's findings and the eventual outcome. In a worst case scenario I've located a tech not too far who has indicated they have a fair bit of experience with Chromas (Backline, in Vancouver). I think for the price I paid even if I have to put a little more in it will have certainly been worth it ;) I'll be compiling a detailed report of my tests of the unit, and the feedback each of you have provided to me, for my local tech to give them an idea of where to start.

I want to again thank everyone for being so helpful. Your step-by-step guides and directions have been very useful, and have really led me to realize I want this Chroma fixed -- not only for the sake of using the Chroma but because this is a community I want to be a part of.

Keyboard-Issues

Werner Schöenenberger [21010114]

Dear all,

again some strange behavior of a Chroma. The keys C and C# one octave above the middle C sound as fully hit and as keeping pressed even when released. It is very strange, that only these two keys have this behavior, the rest of the keys work correct. The PCB with the key switches seems to be correct, the contacts and the corresponding resistor array are correct.

On the I/O board I expect the driver LS244 (Z34) and bank latch LS175 (Z35) working correctly, otherwise I would have key failures on other parts of the keyboard. I also do not expect the address latch LS373 (z32) to be faulty, otherwise the keyboard handling would not work at all. Now my question: Did anybody have issues with the EPROM of the keyboard processor or any other idea to resolve the issue?

Thank you very much in advance.

Paul DeRocco [21030230]

I'm not sure what you mean by your description of the symptoms. And I'm not sure what you mean when you say that the contacts and resistor array are "correct". This sort of problem is almost always dirty contacts. A strip of non-fuzzy paper wet with alcohol inserted between the contacts and dragged back and forth always worked well for me.

Werner Schöenenberger [21010114]

Hallo Paul,

thank you very much for your reply and your support. The contacts are clean and work fine. Finally, I could resolve the issue. I thought that it cannot be the keyboard scanning electronics because there MUST have been some repetitive effects of non working keys. So I re-soldered the resistor array which was the solution. It seems that this Chroma has a lot of soldering issues. The measurement of a closed contact of the working keys returned a resistance of 11.5 kOhm in most cases, while the resistance of the faulty keys was 10.81 kOhm. Surprisingly keys with a resistance in closed position of 10.86 kOhm worked. Weird.

Chroma with CC+ and Pressure Sensor Sold on eBay

Chris Ryan [21030691]

"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. "

Keith Hedger [21030607]

chroma sold on eBay

I bought this Chroma [21030607] and am waiting anxiously for it. Personally I think the price was way too high, but the market says it was a pretty good deal (based on the 5k and 6k machines I've seen flying around). I look forward to re-joining the Chroma community....

firmware update 215, pressure sensor board unglued

Brian McCully [21030361]

Finally got a chance to update to the latest [CPU Plus] firmware and call up a bunch of set split 38 randomizer patches - really a lot of fun. What an awesome sound generator! Lot of noise generation in the patches, but the envelopes really do some neat things. Can't wait to get some kind of GUI editor happening to see what's making up these sounds - it's very intriguing. Thanks again for the update, David.

Also, I hadn't played the Chroma in a while due to other projects, and I still needed to remove the felts under all the keys to work more properly with the pressure sensor installed (new as of last December), so I was waiting to upgrade the firmware, and to do these other little maintenance things. Unfortunately when I went to work on the Chroma I found that all of the keys were hard to press down. Upon opening, discovered that the pressure sensor strip had come undone, and was flopped down on the back of the keys. It was separated between its long sensor circuit strip and its board above it. I have emailed Chris Borman [21030194+] asking about how to go about re-adhering it (in a more permanent fashion).

Other than the adhesive not being strong or lasting enough, it might have something to do with the front panel lip possibly pressing against the connector on the front of the upright pressure sensor card, causing a slight 'pry-away'. So I filed away more of a gap in the lip, to add more clearance for the times that the front panel is removed (and flipped up, etc.) I'm pretty sure the gap I made prior, had had enough clearance, but don't want to chance anything when I have to go under the hood again. One needs to be really cautious jockeying around the front panel, with that upright pressure sensor card installed in place - its connector juts out, necessitating the front panel upper (and inner) lip to be cut away on the inside. (I really do wish that card was not on the front side).

Also - I did remove all the front felts and now the pressure sensor works better (100%) with them gone (whereas before, I had two notes that weren't fully operative with the felts in place). Overall the key action is just as fine - very Chroma!

Chris Borman [21030194+]

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. Don't think the FP could have pushed just the PCB off (as the photos you sent clearly indicate) rather, the entire assembly would have dropped. Sounds more like the guy doing CPS fabrication wasn't paying attention again... I won't mention any names.

The mux bd is what is is for now, but I am making a Rev 3 controller that along with a new sensor array will both have smaller dimensions and less in-between cabling to allow installation into other keyboard actions. There will be various interfaces and will probably include a J22 Chroma or 'legacy' port if you will through software.

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?

Jeffrey D. McEachin [21030073+]

At 01:23 PM 7/31/2011, Brian McCully wrote:

Unfortunately when I went to work on the Chroma I found that all of the keys were hard to press down. Upon opening, discovered that the pressure sensor strip had come undone, and was flopped down on the back of the keys. It was separated between its long sensor circuit strip and its board above it.

The same thing has happened to mine. :(

Other than the adhesive not being strong or lasting enough, it might have something to do with the front panel lip possibly pressing against the connector on the front of the upright pressure sensor card, causing a slight 'pry-away'. So I filed away more of a gap in the lip, to add more clearance for the times that the front panel is removed (and flipped up, etc.) I'm pretty sure the gap I made prior, had had enough clearance, but don't want to chance anything when I have to go under the hood again. One needs to be really cautious jockeying around the front panel, with that upright pressure sensor card installed in place - its connector juts out, necessitating the front panel upper (and inner) lip to be cut away on the inside. (I really do wish that card was not on the front side).

I have to agree, the board mounting is quite awkward. I showed it to a friend and his comment was "that board could have been so much smaller with surface mount! It's not that hard to solder!"

I'm hoping, though, that I won't have to "go under the hood" too often, in which case it'll be a mostly moot point.

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