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ChromaTalk Archives: December 2011

Warranty Card

Chris Ryan [21030691] · Sun, 4 Dec 2011 13:58:36 -0800

New on the site this month: scans of the Chroma warranty card. Thanks to Odysséas Tsakas-Grigoriadis [21010242] for this contribution.

Re: More Manuals and Computer Interface Software Disks on eBay

Go to first message in thread, November 2011

Chris Ryan [21030691] · Sun, 4 Dec 2011 22:00:27 -0800

On 15/11/2011, at 8:23 AM, Chris Ryan wrote:

Performance Manual (spiral bound--perhaps a photocopy), item #170729195523, USD$29.95.

Was re-listed as item #180764691891 and sold for USD$16.00.

Chroma on eBay Germany

Chris Ryan [21030691] · Mon, 5 Dec 2011 08:49:50 -0800

Via "Johnny Vintage:" item #190610383469, starting bid €4,000.00, no bids yet, ends December 11. I've asked for pictures and serial number. Google translation of the description: "Sell ​​for one of our keyboardist Rhodes Chroma synth (no midi), good condition. Collection - no shipping! PRIVATE SALE NO WARRANTY and WARRANTY, NO RETURN!"

Jesper Ödemark [21010135] · Mon, 05 Dec 2011 19:31:26 +0100

Köln (Cologne) as home town. My Chroma was originally sold there. :)

Jesper Ödemark [21010135] · Sun, 11 Dec 2011 13:18:26 +0100

worst Chroma auction in years?

[Re-posted eBay item #190610383469]

No photo, short descrition and still no bargain price.

Rob Belcher [16330123] · Sun, 11 Dec 2011 14:27:32 +0000

Re: worst Chroma auction in years?

Sadly there are no more bargain any more jesper :(

Matt Hillier [21010094+] · Sun, 11 Dec 2011 15:26:18 -0000

Re: worst Chroma auction in years?

without a doubt the worst i have ever seen or not.....even if it was a scam the guy would have made the effort to at least download an image from yahoo images.It makes you wonder what the guys trying to achieve.Sell it ? really ?

the basic rule if selling anything is image......good images and then good description that sells.

Its like me saying

' Roland jupiter 8 for sale ' no images, haventa clue what it sounds like , it might be a synth , it may exist ? it may work ? it may not but for £5000 or best offer i am happy to sell you what i cant be bothered to advertise properly.....

that suggest more about the person selling than the synth to me and with that ' level ' of advertising skill you know this synths possibly going to be a piece of junk or something relative to its ' owners ' mentality ........people read that ad and go ' yeah right ' see you later .

On the other hand sometimes these types of ad are the result of a disfucntional synth freak who spent years with the synth or what he is selling in bubble wrap and theres a good synth beneath the Idiocy of the ad.

Either way i dont like these prices even though i still have a Chroma , Inflations destructive on some level and i saw this with Ems stuff and its killed the true nature of the machine and the wrong type of people are now fixated on them and using them like ' high interest rate accounts ' .That for me is very sad.

Ebays a very destructive force .

On a more postive not its a lovely day here.

Arun Majumdar [21030348] · Sun, 11 Dec 2011 11:42:02 -0500

Re: worst Chroma auction in years?

I don't think the seller wants to sell it (though maybe someone else is requesting it get sold --- the seller would have a really bad advert like this to avoid it actually being sold).

Frank Hettlich [21030041+] · Sun, 11 Dec 2011 18:14:21 +0100

Re: worst Chroma auction in years?

I do think the seller wants to sell but you underestimate the laziness these days.

Many ebay offers today are even created by ebay mobile with rudimentary infos...and they sell! Probably for less but they don´t care...

And it seems that this guy knows how easy it seems to be to get rid of a Chroma without any effort. His effort is near zero as we all agree here but it might be enough to attract potential buyers.

People don´t care about each other any more...luckily there are exceptions like Peter Forrest and a few others!

I recently made a deal but later the seller backed out because he was too lazy to pack the device (a drum machine!) and gave precedence to someone else who would collect it in person.

All the best to the remaining good guys - lots of them here on the list

Jack Colburne [21030142+] · Sun, 11 Dec 2011 14:37:13 -0500

Re: worst Chroma auction in years?

Frank: "I recently made a deal but later the seller backed out because he was too lazy to pack the device (a drum machine!) and gave precedence to someone else who would collect it in person."

Chroma 21030737 on eBay

Chris Ryan [21030691] · Mon, 5 Dec 2011 17:52:44 -0800

Item #300633209498, USD$4,999.00. From the description: "With Syntech MIDI and more. The unit has been fully serviced to be 100% functional and is in nice cosmetic condition as well. It will come as shown below in the pics so take a peek. This piece has been tested and is guaranteed to be in proper working order or your money back!" Also comes with the Chroma binder; I have this as an original owner but I haven't seen many of them over the years.

21030737 is new to the registry.

Chris Ryan [21030691] · Thu, 8 Dec 2011 16:58:54 -0800

Sold at the asking price.

Chris Borman [21030194+] · Thu, 8 Dec 2011 20:44:47 -0500

If you want to pay top dollar, that’s the goto ebay store. Always has nice photos though!

Matrix [21030220] · Thu, 8 Dec 2011 17:58:26 -0800

I think it depends on the item with them. They do have some really good prices. I picked up a Prophet VS Rack from them recently at what I though was a great price considering there aren't many of them out there. I created a TouchOSC template for it BTW.

The one thing with a dealer is they have a reputation to uphold, so the item is more likely to be in the condition described and should anything go wrong they will more likely make it right.

Chris Borman [21030194+] · Thu, 8 Dec 2011 21:11:05 -0500

A good place to buy stuff for sure. That SCI VS is a GREAT synth. Excellent design and phenomenal sound in the right hands. For me everything I want is high priced, and everything I sell brings low dollar in ebayland...

Re: Poly Pressure Via MIDI

Go to first message in thread, October 2011

Jesper Ödemark [21010135] · Wed, 07 Dec 2011 14:17:54 +0100

David Clarke skrev 2011-10-06 04:27:

If you're using the CC+ for MIDI:

  • Ensure that firmware version 213 or newer is installed (checked via [SET SPLIT 36][P25])
  • If firmware 215 is being used, ensure Polyphonic pressure mode is selected [SET SPLIT 36][P16] = Pol.
  • Ensure that MIDI Pressure Tx is enabled [SET SPLIT 36][P26] = On.

Long time now but I realised I never thanked for the help. So, thanks. It works like a charm now. :)

Sequencer Manual on eBay

Chris Ryan [21030691] · Sat, 10 Dec 2011 12:27:28 -0800

Item #170745589653, USD$29.95, ends December 16. Titled "Model 1611 Computer Interface Service Manual," it's actually the Sequencer Manual, Rev 5, in a Chroma binder. The description says, "all of our manuals are new/old stock, real and not reprints."

This manual is available at the site in scanned PDF format; in addition a couple of years ago I posted Appendix O, Hardware Description and Specifications, in HTML along with high quality PDFs of the schematic and compont layout drawing.

Pictures from the auction:

170745589653a

170745589653b

Go to next message in thread, January 2012

Re: WTB Chroma voice boards

Go to first message in thread, November 2011

David Clarke [21030085++] · Sun, 11 Dec 2011 14:21:28 -0500

... Would anyone of you have a few spare voice boards that he would think of selling ? If yes you can email me off list and tell me how much you want for them.

Following up to this trail from the end of November, I know that at least one other member of this list built up some voice board circuit boards from the data from the site (see Building New Voice Boards).

For those folks that might want to try to build their own, but don't want to go through the trouble of getting a circuit board created, might there be any extra 'blank' boards available to members of the group?

Greg Montalbano, Analog Synthesizer Service · Sun, 11 Dec 2011 13:10:56 -0800

I still have two, from a batch I had made up several years ago -- these are from your specifications, as posted on the site. You might want to advise anyone trying this that it's not a beginner project -- care, judgment, patience and the willingness to troubleshoot are required.

Anyone interested in the boards can contact me off list.

Jeffrey Koepper [21030671] · Sun, 11 Dec 2011 17:08:28 -0500

chroma voice boards for sale-

HI I may be selling some Chroma voice cards. I no longer have a chroma and these were spares for me. All voice cards are complete and are not missing any parts. These are sold as-is as I have no way of testing them. contact me at [email address removed] for more info.

John Leimseider [21030434++] · Sun, 11 Dec 2011 15:12:18 -0700

I talked to a few people about the fact that I have 5 spare working boards. These are all boards that I repaired, so they do have some socketed ICs, plus whatever other repairs were needed. I did get 2 Emails about them, but I lost the addresses. So, if people are interested in them, they are $275 each including shipping to the US and Canada, or plus shipping to anywhere else... To the 2 guys who Emailed me previously, sorry, please send me your messages again and you can have the first dibs on them, if you want. I will have a couple more when I finally fix them, alos. Thanks!

Re: Alternate Displays to use with CC+ Alphanumeric Display Capability?

Go to previous message in thread, November 2011

David Clarke [21030085++] · Sun, 11 Dec 2011 15:46:12 -0500

Following up to this earlier thread [October, November]:

  1. Are there any other backpack/serial controllers that others would prefer/suggest over the SparkFun model?
  2. I do have a beta version of firmware to support the SparkFun controller. If there are people who'd like to get the controller/display for experimentation, get in touch with me via e-mail and I can share the firmware image with you. (If we agree the controller operation is sufficient for general use, then the SparkFun selection can be made a formal addition in the next official firmware release.)

(A picture showing representative output of the controller/display noted in the original e-mail is attached.)

red

Frank McGing [21010198] · Sun, 11 Dec 2011 23:07:26 +0000

That looks great David! Are there any display limitations compared to the Parallax? I have a Parallax display here and I'm just waiting to get firmware 215 burned onto an EPROM before I plug it in. I would be much happier with red on black!

Is there much wiring to be done between the SparkFun controller and the display module? One advantage of the Parallax is the simplicity when connecting it.

Great work, as always!

David Clarke [21030085++] · Sun, 11 Dec 2011 20:53:21 -0500

... Are there any display limitations compared to the Parallax? ... Is there much wiring to be done between the SparkFun controller and the display module? One advantage of the Parallax is the simplicity when connecting it.

Frank - if you look at the back of the Parallax display, you'll see the rectangular display proper and a small circuit board soldered on to it.

That soldered-on circuit board is a serial-to-parallel converter - the piece that converts the serial data into something that the display can understand.

The SparkFun controller is effectively that little circuit board - it is a generic serial-to-display controller.

While the Parallax display has the convenience effectively of 'plug and go', the SparkFun approach allows a user to chose the display they want, and then mate it with the controller.

That means there are two additional (initial) steps required with the SparkFun controller (vs. the Parallax display).

First - the user will need to solder it to the display module (or - I suppose if one preferred - you could attach it with wires).

Second, the SparkFun controller is generic and can be used with LCD displays from 16x2 to 20x4. That means a few commands will need to be sent to the device to set it up (e.g., to tell it to run in 20x4 mode, 19,200 baud, etc.)

Once the SparkFun controller is soldered on and configured - it can be thought of as being 'equivalent' to the Parallax approach.

Frank McGing [21010198] · Wed, 14 Dec 2011 14:32:03 +0000

On 12/12/2011 01:53, David Clarke wrote:

...there are two additional (initial) steps required with the SparkFun controller (vs. the Parallax display).

First - the user will need to solder it to the display module (or - I suppose if one preferred - you could attach it with wires).

Second, the SparkFun controller is generic and can be used with LCD displays from 16x2 to 20x4. That means a few commands will need to be sent to the device to set it up (e.g., to tell it to run in 20x4 mode, 19,200 baud, etc.)

Once the SparkFun controller is soldered on and configured - it can be thought of as being 'equivalent' to the Parallax approach.

Thanks for the info David! Apologies for the late reply - my internet connection has been down for the last couple of days...

Regarding the commands to be sent to the SparkFun controller, would this be done from a PC serial port?

David Clarke [21030085++] · Wed, 14 Dec 2011 20:48:50 -0500

Regarding the commands to be sent to the SparkFun controller, would this be done from a PC serial port?

Yes, but...

The "but" is because the display is designed to be connected directly up to a controller, not to a PC's serial port. The upshot of that is that the "data" line is the inverse of what it should be.

So - if you want to hook the display up to a PC to pre-configure it you'd want to put together a little circuit with an 'inverter' to flip the sense of the Tx serial line from the PC's serial port.

Frank McGing [21010198] · Fri, 16 Dec 2011 02:29:49 +0000

On 15/12/2011 01:48, David Clarke wrote:

So - if you want to hook the display up to a PC to pre-configure it you'd want to put together a little circuit with an 'inverter' to flip the sense of the Tx serial line from the PC's serial port.

Hmm, circuit design is definitely beyond the scope of my knowledge! Is there a simpler method for pre-configuring the controller?

Chris Borman [21030194+] · Thu, 1 Jan 2004 01:48:55 -0500

Add a 74HCT04 inverter in the TX line? Why are we discussing a PC connection?

See thread CC+ alternate displays revisited, March 2012

complete set of keys for rhodes chroma for sale

Jeffrey Koepper [21030671] · Sun, 11 Dec 2011 18:08:39 -0500

HI I have a set of keys from a rhodes chroma, they are in great condition, Not sure what to ask so Make an offer on full set. Would rather not sell individual keys. email [address removed]

Jeffrey Koepper [21030671] · Sun, 11 Dec 2011 19:30:56 -0500

chroma keys sold

the set of keys has been sold. thanks

Paul DeRocco [21030230] · Sun, 11 Dec 2011 18:21:24 -0800

Re: chroma keys sold

Just curious, what happened to the rest of the instrument? In particular, the keybed and keyswitches?

Jeffrey Koepper [21030671] · Sun, 11 Dec 2011 21:34:10 -0500

Re: chroma keys sold

HI I never had the keybd, but I do have the 2 key switch boards.

Re: Chroma(s)

Luca Sasdelli [21010226] · Tue, 13 Dec 2011 22:13:01 +0100

I'm just thinking in redoing the EQ board: Heinz already did it, with the added value of using modern VCAs thus saving the two existing CEM3360 for future DVB repairs. The EQ Heinz made has a provision for an external phone amp connection, while I'd like to embed it on the EQ board itself too.

The new EQ board could be built in a way to leave room just below the tune/tone/volume sliders, allowing the LCD being installed there (so Z1, Z2, P4, P25 etc should be relocated somewhere on the board).

The suggested Satistronics HD44780 is 60mm in height, with viewing area of about 40mm and the space below sliders is about 50mm. Maybe try to use a slightly thinner LCD? Or alternately a 40x2 characters instead?

It should be carefully investigated, but I hope it would be a good solution for the LCD.

About the counter-screws for the front panel, no ideas; it's a common component for standard wood hobbysts, but not in inches here in Europe.

I extend the mail to list, should it give some ideas to anybody :)

Following are messages from the off-list thread that Luca forwarded in his post.

Il 13/12/2011 20:44, Phil a ha scritto:

Thanks for the link, however the more I think about it the more I am attracted to the red oon black LCD. Did you ever think of making a hole in the control panel the size of the LCD ? Do you think it could work ?

Also, did you find a source for the round metal piece at the end of the screw as shown in my attached picture ? I need 3 of these (among others...)

Date: Tue, 13 Dec 2011 19:15:51 +0100
From: Luca Sasdelli
To: Philippe [21010227]
Subject: Re: Chroma(s)

Ciao Phil,

the box is here http://it.rs-online.com/web/p/products/219-346/ There is enough room to hold both LCD and MIDI ports, and the CC+ MIDI cable has three extra wires useful to connect the LCD.

Inside of the box cover, there is a sort of grid with same height of the LCD, thus helping in doing the hole.

Il 12/12/11 14.26, Phil a ha scritto:

Ciao Luca, me again.

I was wondering if you had a picture available of your RS-components plastic box housing both your MIDI ports and LCD set on top of your Chroma. That would give me an idea of how to set mine...

Date: Fri, 2 Dec 2011 12:50:39 +0100
From: Luca Sasdelli
To: Philippe
Subject: Re: Chroma(s)

Ciao Phil,

the link you provided gives "part not found"; anyway, the screws I've chosen are with Allen head, while the originals are with Phillips head. The common size is in inches.

At present I can't remember where I've bought the two LCDs, but the pricing was really good. If you're considering the LCD, I suggest to wait for David Clarke to finish his contest about the parallel LCD, so that some red-on-black models would be used instead of the serial driven one, so it would be possible to choose between lots of different display type and manufacturers.

The serial LCD is not that diffused and there is a current factor that limits the choice to a very few models.

Il 02/12/11 11.23, Phil a ha scritto:

Hi Lucas,

Thanks for the details but it seems they are different from the ones on the original Chroma so I am not sure which one is for which place. I have found those here which seem to be very close to the originals : [invalid search results url from Digikey removed]

And might maybe order from them. By the way, where did you bought your LCD display for your Chroma ?

Date: Mon, 28 Nov 2011 18:35:54 +0100
From: Luca Sasdelli
To: Philippe
Subject: Re: Chroma(s)

Hi Phil,

indeed, for Europe this is a real mess. I've purchased some suitable screws from USA, but I've found them online only by a big seller (www.mcmaster.com) that supports overseas sales only for huge quantities, so there has been a volunteer Chroma user in California that bought 'em for me, and then has re-shipped them in Italy.

To keep the discussion clean and calm, I'll pass over the total cost of those @#$"! screws.

The articles are as follows:

Line Quantity Item   Ships Unit Price Total Price
1 1 Pack 91253A153 Alloy Steel Flat Head Socket Cap Screw 6-32 Thread, 1" Length, Black, Packs of 25 after the holiday $10.11 $10.11
2 1 Pack 91255A153 Alloy Steel Button Head Socket Cap Screw 6-32 Thread, 1" Length, Packs of 50 after the holiday $9.61 $9.61
3 1 Pack 96006A253 Black Oxide 18-8 SS Socket Head Cap Screw 6-32 Thread, 3/8" Length, Packs of 50 (Same as 96006A555) after the holiday $5.16 $5.16

The flat-head screws are for the upper panel fixing, while the button-head ones for front panel holders; all of them fits fery well as per my personal taste (see attached image).

Il 28/11/11 17.24, Phil a ha scritto:

By the way, I have many missing screws on the Chromas. Would you have located a good source for the different screws present in the Chroma ?

From: Philipppe
To: Luca Sasdelli
Subject: RE: Chroma(s)
Date: Mon, 28 Nov 2011 16:30:02 +0100

OK. Please do keep me informed !

Date: Mon, 28 Nov 2011 16:29:07 +0100
From: Luca Sasdelli
To: Philippe
Subject: Re: Chroma(s)

Ciao Phil,

unfortunately I don't own any spare voice board; at present I'm building the Chroma DVB Tester to repair them without the instrument. Eventually (and hopefully...) I would repair some boards for you, if the damn box will work.

Il 28/11/11 16.26, Phil a ha scritto:

Hi Luca,

Well, I am currently in the process of trying to revive them. Would you have any voice board for sale yourself ?

Date: Mon, 28 Nov 2011 16:22:13 +0100
From: Luca Sasdelli
To: Philippe
Subject: Chroma(s)

Hi Phil,

just seen your mail to list [WTB Chroma voice boards]. Do you have some news about the Chroma purchase we discussed some time ago?

Power supply problems SOLVED

John Monforte · Wed, 14 Dec 2011 11:46:05 -0500

I am a tech that was given a deceased Chroma to work on. As is all too common, the power supply was kaput.

Look, the design of the supply is terrible, but that is understandable if you consider the conditions it was designed in. When your company is on the skids and you need to get a new product out the door fast, you have to focus on the new stuff (the synth) and mundane things like a power supply can be shoved off as long as it works "well enough".

The problem is, in a nutshell, the supply uses parts at the limits of their capabilities and runs so hot - to the point that parts get roasted.

As I dig through this website, it becomes apparent that Chroma users have apparently struggled with power supply problems since the product was first introduced. Quite a few remedies are shown here on the site and each has its own shortcomings.

One solution, Don Tillman's "nuclear option" replaces the supply entirely. Sure it works, but it is expensive, complicated and clunky.

Other solutions are less effective. They usually involve putting in more sturdy parts that remove them as the weak link in the chain - leaving some other part to be the new weak link. Sure, you can replace the 12 volt regulator with a sturdier part, but the reason it is in distress is because it gets bolted to a "heat sink" that is actually a heat source. The 5 volt regulator puts out so much heat it dries out and burns up other parts that are otherwise being used well within their specifications. Another approach is to replace everything, so all the roasted weak old parts are renewed. This simply resets the clock on the ticking time bomb.

Lets look at just what the problem is. The designers used a transformer that has only one set of secondaries for all the voltages. The largest current demand is from the lowest voltage, the 5v one. It is about 2 amps. Every amp of this current must flow throughout the supply, so everything upstream is pushing the same current, plus whatever is needed for the other voltages. The raw source voltage is about 20 volts - four times larger. That means for every watt delivered to the synth's 5 volt electronics four times as much power has to be burned off by the parts upstream. Add to that the power needed for the other voltages which is smaller but not zero. In order to burn this off more responsibly, they use a "pre regulator". That is not because the real regulator needs a regulated source, it is because some of the burn off can be done on more parts to spread out the places to make heat. Even the power transformer runs hot because it has to deliver so much power.

Another typical side effect of using too high a source voltage for a regulator is RF emission. But apparently that does not seem to bother the Chroma.

The solution to all this is to provide the 5v regulator with a lower source voltage. Replacing the transformer would be a good choice if you are the manufacturer and can get one custom made to your specs. For us the answer is a second transformer with a lower voltage secondary. I picked a Triad VPT18-1390 which is a stock item from Digi-Key. This transformer is small enough to fit on the back panel. It has international primaries so they are hooked up along with the other transformer's primaries so the voltage selector still works. CR1 and CR2 are disconnected from the board at the anode ends and the secondaries of the new transformer are connected there. Nothing else needs changing.

Done.

The new transformer is less wasteful of power so the 5v stuff runs cooler and, by extension, everyone else is cooler too. The old transformer now has an easier job, dealing only with the other voltages. It is coasting at a fraction of the power it had before. You can put your hand on the back and feel some warmth. Before, you needed to be a Swami to leave your hand there.

So far so good. Now my attention can be diverted to other problems in this unit (and there are a few more). I am getting stumped, so you will hear about this in another set of posts. I'm going to need to tap into your collective expertise to get this unit totally functioning again.

John Monforte · Wed, 14 Dec 2011 11:48:28 -0500

The picture

I forgot to attach the photo. Here it is!

powertransformer

Dave Bradley [16330135] · Wed, 14 Dec 2011 11:07:58 -0600

Re: The picture

Interesting solution.

Russ Lyons [21030574] · Wed, 14 Dec 2011 13:50:14 -0500

Re: The picture

See, even the Chroma gains weight during the holidays!

Nice, quick fix, but it was $20 plus shipping just for one item and I know from experience, "Just replace the whole supply with a modern one", for reasons posted by all others. I used Don Tillman's solution for the most part. Putting a nice $100 Power-One supply in a now $4000 synth seems to be a great investment.

Most synths I've fixed had power supply problems. For some reason ($$$ and nearsightedness) manufacturers cut corners on the most important part of an electronic design.

Thanks for the failure analysis. sharing and photo.

Does someone have the dimensions of the expander case?

Doug Wellington [21030300] · Thu, 15 Dec 2011 14:19:40 -0700

I did a quick search (yeah, too lazy to do anything more than that) but I didn't find the info I'm looking for. Can someone tell me what the dimensions are for the Chroma Expander? I'm mostly interested in the side panel, that is, what is the height, angle of the front panel, and the front to back distance of the top and bottom? (I Assume that the width is the same as the Chroma itself...)

David Clarke [21030085++] · Thu, 15 Dec 2011 19:57:02 -0500

Looking at the right wooden end-cheek you'll see something that looks like the following bad ASCII drawing: 

                        A
                -------------------------
             /                           |
     E    /                              |
       /                                 |  B
    /                                    |
  |                                      |
D  |                                      |
  ---------------------------------------
                     C

With dimensions close to:

  • A = 7 13/16"
  • B = 6 1/16" (same as the equiv. measurement on the Chroma)
  • C = 11 13/16"
  • D = 2 1/8"
  • E = 5 9/16"

(The drawing doesn't reflect the fact that the 90 degree corners are not actually 90 degree corners and are 'chopped off', like they are on the Chroma too))

The 'shipping' dimensions would be bigger in the "B" direction - because there are feet on the bottom (like the Chroma).

Doug Wellington [21030300] · Thu, 15 Dec 2011 21:46:28 -0700

Fantastic, thanks so much! I don't have an expander yet (and may never get the chance, who knows), but now I can make my own add-ons and keep to the form...

CPS kit

Chris Borman [21030194+] · Thu, 15 Dec 2011 23:21:41 -0500

I have accumulated a pile of misc. key pressure hardware parts that have gone idle so it's time to dump it all. Last chance to get a Chroma Rev 2 CPS kit. Please give thanks to all the folks who paid up front before the design was complete. This would have never happened without their support. And don't forget those who paid top dollar for their kits and struggled through installation. Nothing like field experience. We all worked through various issues so it seems we have a stable product at this point. Send ME an email if interested.

New voice cards?

Doug Wellington [21030300] · Mon, 19 Dec 2011 10:37:27 -0700

Happy holidays everybody!

I'm planning projects for next year and the one I keep thinking about is to design a new voice card for the Chroma without the hard-to-find CEM chips. Is anyone else already working on this?

Paul DeRocco [21030230] · Mon, 19 Dec 2011 09:59:24 -0800

Not me, but I'd be happy to look over your design, and maybe help out, since I designed the original ones.

Doug Wellington [21030300] · Mon, 19 Dec 2011 11:28:48 -0700

Very cool, thanks! Funny, I think the hardest thing is going to be deciding what filter and vca designs to use. While it would be great to duplicate the Chroma sound, I'm not necessarily stuck on that idea. I'm more interested in having fun, experimenting and coming up with something that works, with parts that are more easily available.

I have a bunch of 2044 chips already, so that's a possibility, but part of me thinks it would be good fun to play around with some designs without dedicated filter chips.

On a different path, I also have a couple PA397 chips, so it might be interesting to see if I could come up with a design for them as well..

FWIW, I'm an Eagle guy...

Luca Sasdelli [21010226] · Mon, 19 Dec 2011 19:50:27 +0100

Excellent!

The only critical components seems to me being the dual VCF CEM3350 and the Tempco resistors XR4151, LM393 and logic ICs are still common and cheap components NTE912 is a pin-to-pin replacement for the CA3086 SSM3124 or THAT2162 could replace CEM3360 4558 and signal-path TL082 could be replaced with TL072, OPA2134A etc. TL082 S&Hs could be grouped within TL074s or even a TLC274x2, TL074x2 (8x OAs)

Heinz [21010276] defined a way to assemble suitable tempco resistors Moreover, Digikey has some surface-mount Tempco 3300ppm/°C at reasonable price

About the CEM3350, I guess that a candidate is the CEM3396, used on DS Prophet 08 and OB Matrix 1000 expander, but it is single channel.

A new voice card, indeed, should include a redesigned Channel Motherboard, possibly with better DVB connectors (!) and panned stereo output. The noise generators 2688/5837 should be replaced with a zener diode :-)

A terrific challenge!

Jesper Ödemark [21010135] · Mon, 19 Dec 2011 20:24:52 +0100

Doug Wellington skrev 2011-12-19 19:28:

---I have a bunch of 2044 chips already, so that's a possibility, but part of me thinks it would be good fun to play around with some designs without dedicated filter chips.---

FWIW, I'm an Eagle guy...

OK, call me crazy, but this is how the EDP collector works: "Eagle" was the planned polyphonic version of the Wasp. It never made it onto the market though. The Wasp is theeee coolest monophonic around. The filter and VCA is amazing too. Also cheaply done around standard components. I'd love a Waspified Chroma. Or maybe a chromed Wasp. %-)

OK, time for this swede to shut up! :D

Paul DeRocco [21030230] · Mon, 19 Dec 2011 12:09:47 -0800

From: Luca Sasdelli

The only critical components seems to me being the dual VCF CEM3350 and the Tempco resistors XR4151, LM393 and logic ICs are still common and cheap components NTE912 is a pin-to-pin replacement for the CA3086 SSM3124 or THAT2162 could replace CEM3360 4558 and signal-path TL082 could be replaced with TL072, OPA2134A etc. TL082 S&Hs could be grouped within TL074s or even a TLC274x2, TL074x2 (8x OAs)

Heinz defined a way to assemble suitable tempco resistors Moreover, Digikey has some surface-mount Tempco 3300ppm/°C at reasonable price

As long as you can get a resistor with a positive tempco of at least 3300ppm, you can pad it down with a parallel resistor.

About the CEM3350, I guess that a candidate is the CEM3396, used on DS Prophet 08 and OB Matrix 1000 expander, but it is single channel.

I'd stay away from any CEM chip, since they're not making any more of them.

A new voice card, indeed, should include a redesigned Channel Motherboard, possibly with better DVB connectors (!) and panned stereo output.

Panned stereo controlled by what in the software?

The noise generators 2688/5837 should be replaced with a zener diode :-)

Or a much longer pseudo-random sequence.

Dave Bradley [16330135] · Mon, 19 Dec 2011 14:33:19 -0600

I'd stay away from any CEM chip, since they're not making any more of them.

Not to mention that the DSI filters are not beloved for their sound. You don't want to make a voice card that sounds worse!

Doug Wellington [21030300] · Mon, 19 Dec 2011 13:47:49 -0700

Hiya Dave,

Not to mention that the DSI filters are not beloved for their sound. You don't want to make a voice card that sounds worse!

Definitely do not want worse! :) Too bad Juergen [Jürgen Haible] left us already, it would have been fun to work with him on filters for this project... :(

Eric · Mon, 19 Dec 2011 21:59:09 +0100

Better have the OB1 or OBX discrete filter design with access to each mode. But it uses CA3080 which also became rare…

Doug Wellington [21030300] · Mon, 19 Dec 2011 14:56:24 -0700

Hiya Eric,

Better have the OB1 or OBX discrete filter design with access to each mode. But it uses CA3080 which also became rare

I suppose that begs the question of how many of these things I/we would produce... I probably have 250x 3080 chips, 100x 3280, a couple score 2044, etc...

Regards, Doug (Should I plan to make expander chassis as well?)

Dave Bradley [16330135] · Mon, 19 Dec 2011 16:16:35 -0600

On Mon, Dec 19, 2011 at 2:47 PM, Doug Wellington wrote:

Too bad Juergen left us already, it would have been fun to work with him on filters for this project... :(

Oh my gosh, I hadn't heard. That's terrible news! Such a tremendously talented guy.

Paul DeRocco [21030230] · Mon, 19 Dec 2011 14:21:55 -0800

From: Doug Wellington

I suppose that begs the question of how many of these things I/we would produce... I probably have 250x 3080 chips, 100x 3280, a couple score 2044, etc...

One problem is that if the board sounds at all different, it will be necessary to sell sets of eight, which could get very expensive. On the other hand, if they sound the same as the old ones, selling them as onesies means they wouldn't be all that price-sensitive, compared to the calculations we had to make in the original design. That suggests to me that it is important to duplicate the sound of the original.

Doug Wellington [21030300] · Mon, 19 Dec 2011 15:36:55 -0700

Hiya Dave,

Oh my gosh, I hadn't heard. That's terrible news! Such a tremendously talented guy.

Yes, and only 47... :(

Maybe he's hanging with Larry... :)

Doug Terrebonne [21030114] · Mon, 19 Dec 2011 14:48:10 -0800

One problem is that if the board sounds at all different, it will be necessary to sell sets of eight, which could get very expensive. On the other hand, if they sound the same as the old ones, selling them as onesies means they wouldn't be all that price-sensitive, compared to the calculations we had to make in the original design. That suggests to me that it is important to duplicate the sound of the original.

I don't think you'll match the sound of the originals without the CEM3350 so that would mean replacing all 8 at once... Now a separate complete expander might be interesting...

Doug Wellington [21030300] · Mon, 19 Dec 2011 15:57:28 -0700

Hiya Paul,

One problem is that if the board sounds at all different, it will be necessary to sell sets of eight, which could get very expensive. On the other hand, if they sound the same as the old ones, selling them as onesies means they wouldn't be all that price-sensitive, compared to the calculations we had to make in the original design. That suggests to me that it is important to duplicate the sound of the original.

That will be interesting. Of course, I'm using the original VCO parts, so that shouldn't be a problem, and I figure I can get close with the VCA, but the filter? Hmmm...

At the same time, looking at the prices from the last batch of voice boards, $50 of the $140 was for the CEM chips, so I would hope the price would be less than the last batch.

Jesper Ödemark [21010135] · Tue, 20 Dec 2011 00:08:14 +0100

Doug Wellington skrev 2011-12-19 23:57:

At the same time, looking at the prices from the last batch of voice boards, $50 of the $140 was for the CEM chips, so I would hope the price would be less than the last batch.

As long as there surfaces corpses of Chromas here and there at at least reasonable prices I fear it's no big business in cloning voice boards.

Luca Sasdelli [21010226] · Tue, 20 Dec 2011 04:59:19 +0100

'Il 19/12/2011 21:09, Paul D. DeRocco ha scritto:

I'd stay away from any CEM chip, since they're not making any more of them.

There should be some quantities of 3396s around and its price isn't that high as per 3340s. The mean reason is the VCF timbre, quite unique about Curtis chips.

Panned stereo controlled by what in the software?

I'm just thinking of some "hardcoded" panning, thus distributing the 8-16 voices across music front. A programmable panning does require further investigation and development within firmware and I'm not sure about its real improvement in respect to the hardware solution.

Or a much longer pseudo-random sequence.

Oh, sure :) Simply I consider the zener noise generation far better than expensive and/or rare chip one. Moreover, at least two pseudo-random generators should be used (as in Chroma) to avoid audible repeating cycle.

Luca Sasdelli [21010226] · Tue, 20 Dec 2011 05:07:14 +0100

Il 20/12/2011 04:59, Luca Sasdelli ha scritto:

Simply I consider the zener noise generation far better than expensive and/or rare chip one. Moreover, at least two pseudo-random generators should be used (as in Chroma) to avoid audible repeating cycle.

Anyway, just as a reference, here is a PIC-based noise generator, originally intended to replace MM5837 in synthesizers: Electric Druid Noise Generator (PDF)

Here the article White Noise Source

Doug Terrebonne [21030114] · Mon, 19 Dec 2011 20:48:49 -0800

On Mon, 12/19/11, Luca Sasdelli wrote:

There should be some quantities of 3396s around and its price isn't that high as per 3340s. The mean reason is the VCF timbre, quite unique about Curtis chips.

The CEM3396 is nothing lke the CEM3350. The 3396 has a single low pass only filter and the 3350 is a dual state variable design. I don't think many people would want the filter of a Matrix-6 and Prophet-08 replacing the original one in their Chromas...

Doug Wellington [21030300] · Mon, 19 Dec 2011 21:55:15 -0700

Hiya Luca,

There should be some quantities of 3396s around and its price isn't that high as per 3340s.

And the two 397 chips I bought were $25 each when I got them. In bulk they're cheaper than that...

Simply I consider the zener noise generation far better than expensive and/or rare chip one. Moreover, at least two pseudo-random generators should be used (as in Chroma) to avoid audible repeating cycle.

I've been using both analog and digital noise circuits in the drum circuits I've been working with. It's not so obvious with the short envelopes, but I really like the analog noise circuits better for longer sounds...

Tom Klepacki [21030025] · Tue, 20 Dec 2011 00:28:05 -0500

Has anybody contacted my nephew's company [ZD Integrated Circuits Inc. - Locations], for a source of chips? This is exactly what he does. They scour the planet for sources of common, and rare chips. New and recycled. And, resell them.

ZD Integrated Circuits, Inc.
Craig Zurman
Corporate Office
12420 73rd Court
Unit B
Largo, FL 33773
[Phone numbers removed]

Tell him his uncle Tom and aunt Chris made the referral. MAYBE he'll give us Chroma owners/ users a good deal? (I hope!)

Paul DeRocco [21030230] · Tue, 20 Dec 2011 09:58:30 -0800

From: Luca Sasdelli

There should be some quantities of 3396s around and its price isn't that high as per 3340s. The mean reason is the VCF timbre, quite unique about Curtis chips.

The timbre of the Chroma filter is also due to the way the resonance feedback is limited.

It should be possible to design a VCF that sounds pretty much exactly like the Curtis chip, but made with discrete matched pairs and op-amps, and a separate expo converter. A lot of parts, but they'd be cheap parts, and in surface mount they wouldn't take any more room than the existing circuit.

Simply I consider the zener noise generation far better than expensive and/or rare chip one. Moreover, at least two pseudo-random generators should be used (as in Chroma) to avoid audible repeating cycle.

We used zeners back at Arp, but they required hand selection to find sufficiently noisy ones, and occasionally one that had put out nice noise would go bad and start putting out erratic, crackling noise, and need to be replaced.

The problem with two PRS circuits running at slightly different frequencies is that every now and then their sequences would roll across each other and you'd hear the flanging effect. Three would probably reduce the statistical likelihood of that to insignificance.

Luca Sasdelli [21010226] · Tue, 20 Dec 2011 19:21:42 +0100

Il 20/12/11 18.58, Paul D. DeRocco ha scritto:

It should be possible to design a VCF that sounds pretty much exactly like the Curtis chip, but made with discrete matched pairs and op-amps, and a separate expo converter. A lot of parts, but they'd be cheap parts, and in surface mount they wouldn't take any more room than the existing circuit.

That's very interesting. Heinz already did a CEM3350 study on this list.

The problem with two PRS circuits running at slightly different frequencies is that every now and then their sequences would roll across each other and you'd hear the flanging effect. Three would probably reduce the statistical likelihood of that to insignificance.

Did you have a look to that PIC-based one? Electric Druid Noise Generator (PDF)

Andrew Howson [21030209] · Wed, 21 Dec 2011 01:56:23 +0000

Hey Doug,

I'd definitely be interested in a new Chroma voice card. I'm actually on the waiting list for another one of your projects, the MB-808 project. You probably better know me by common user name, Selidor, and a different e-mail address I initially signed up through (and still use).

Anyhow, I'd definitely be interested in a complete Chroma voice card clone project, so you can sign me up for that too. I think it might also be possible to build a PCB to be attached to existing Chroma voice cards in order to replace the hard-to-replace CEM chips.

Now my electronic and soldering skills are limited to following instructions, but from what I've been able to gather the Chroma's voice card is not a multi-layer PCB, so it should be possible to drill holes through the PCB at the points that connect with the CEM chips, to the back of the voice card and through a second PCB that has been affixed to the back of the Chroma's voice card, to run a wire or trace through. This second PCB would be placed on top of the traces, effectively covering them up, that are located on the back of the Chroma's voice card. The second PCB could then include discrete components and traces that effectively clone the CEM chips, on one side only because the other side would be placed against the original voice card's traces. The final product would look like two PCB's, one of which would be slightly larger than the other, in order to fit in to the voice card's placement slots, firmly fixed together as one with components on both sides, and one set of traces running through the middle (from the original voice card only). I'm not sure this description is clear, but I can draw up a diagram if not.

During startup the Chroma runs a test on the voice card, including the filter. It might be possible to adapt other filter designs to pass the voice card test and thus be used in the Chroma. Yes, we all love the Chroma's filter -- but I'd gladly buy eight cards to swap with my Chroma from time to time that were based around the EMS diode filter, Korg's highpass and lowpass filters from the MS-20, Dave Rossum's AM8040 lowpass or Roland's AM8109, or -- well, you get the idea.

I guess new filter types would require full voice card clones, as most Chroma users would want to hang on to card that had the original filter designs too. Seeing as how you're proficient with digital designs, at least I presume as much given the needs of the MB-808 project, maybe you could widen the appeal of the Chroma voice card clones by designing a 1U rackmount, with simple controls and emphasis on editing parameters through MIDI, that could house and effectively "run" one Chroma voice card, making a monophonic (or duophonic, depending on the user configuration) Chroma an option for those who don't actually own a Rhodes Chroma.

Anyhow. I'm done rambling. Thanks for your time Chroma-community ;)

Doug Wellington [21030300] · Wed, 21 Dec 2011 02:45:56 -0700

Hiya Andrew,

Thanks for being patient on the MB-808. Looks like I won't get to ship them until after the holidays...

As for new designs, the problem I always have is that there are too many possibilities! :D I'm like Woz, I've got the technical knowledge, sometimes I need a Jobs marketing type to set the parameters (and dumb down the interface for general use)... ;)

Now my electronic and soldering skills are limited to following instructions, but from what I've been able to gather the Chroma's voice card is not a multi-layer PCB, so it should be possible to drill holes through the PCB at the points that connect with the CEM chips, to the back of the voice card and through a second PCB that has been affixed to the back of the Chroma's voice card, to run a wire or trace through.

That is a bit like Brian's x0xi0 mod for the x0xb0x...

During startup the Chroma runs a test on the voice card, including the filter. It might be possible to adapt other filter designs to pass the voice card test and thus be used in the Chroma. Yes, we all love the Chroma's filter -- but I'd gladly buy eight cards to swap with my Chroma from time to time that were based around the EMS diode filter, Korg's highpass and lowpass filters from the MS-20, Dave Rossum's AM8040 lowpass or Roland's AM8109, or -- well, you get the idea.

Yes, it comes down to the question of where to put the effort. For me, I have a decent size (100+ module) MOTM and FRAC analog modular rig, so it's easier and more generally applicable to design and build separate modules behind individual panels. In this case, I plan to build a 4151-based VCO behind a MOTM panel so that I can test various VCF and VCA designs before finalizing anything...

I guess new filter types would require full voice card clones, as most Chroma users would want to hang on to card that had the original filter designs too. Seeing as how you're proficient with digital designs, at least I presume as much given the needs of the MB-808 project, maybe you could widen the appeal of the Chroma voice card clones by designing a 1U rackmount, with simple controls and emphasis on editing parameters through MIDI, that could house and effectively "run" one Chroma voice card, making a monophonic (or duophonic, depending on the user configuration) Chroma an option for those who don't actually own a Rhodes Chroma.

Just between you and me and the fencepost, I've been playing with a design that is sort of like a 500 series lunchbox but for synth voices. (It actually started as a smaller version of the PARIS MEC if you've heard of that.) It should be fairly easy to make a Chroma voice card for it...

searching an I/O board

Daniel Rickenbach [21010172] · Tue, 20 Dec 2011 01:04:28 +0100

Hi

I'm working on a defect chroma. The main problem is the I/O board, which has a lot of damages, caused by a defect memory battery. I tried to resolder the defect areas on the board, but it is more difficult than I thought at the beginning of my work.

To bring back into life my chroma a complete replacement of the I/O board would be very helpful.

Is there any possibility to buy a complete I/O board as spare part for my chroma (and to send it to switzerland)?

The same problem is with the EQ-board, if there also an EQ-board around it would be fine - for the EQ-board there are also alternatives possible, so it's not so important as with the I/O board.

Thanks for your help

The Shipment from Hell!

Luca Sasdelli [21010226] · Tue, 20 Dec 2011 04:46:42 +0100

Hi all,

I've been noticed by a kind USA customer that a shipment with two SPSU kits has been delivered in "only" 7 months, since last May to December :)

This was the main reason making me switch from ordinary post to EMS when shipping to USA: until now, EMS takes about 5-6 days to final delivery.

Therefore, because after the required 3-months waiting for Italian Post response (40 working days allowed for delivery, more 40 working days to wait for answer from USPS...) I've considered it as lost, I've re-shipped two more kits to him: the first package now has appeared "from nowhere" and I'd like to propose the two kits for sale in the USA, thus saving overseas shipping costs.

The kit price is US$ 175,00 each and they are available even for home pickup in CA, as per kind suggestion of the very very patient guy.

Interested users please contact me for infos.

CPS-installation

Claes von Heijne[16330008] · Wed, 21 Dec 2011 09:46:32 +0000

Hello list,

I follow the ChromaTalk, but seldom jumps into it. Now it seems I have a problem with the CPS. It's installed by my very skilled tech together with 2.13-2.14 eproms. This is what comes up; "Both the Chroma and the Expander works through midi, but no sound comes out. Aftertouchsensors can be measured to work, but there is no indication of midi-out from them either" At this point I do not know if he has done (set split) 36 and P17, P22 respectively, but since he made the heart- and brain-installations perfectly I have little hope it's that simple.

Has anyone had these problems with the CPS-installation?

thanks

chromaface and possibly a chroma on Ebay Germany

Jesper Ödemark [21010135] · Wed, 21 Dec 2011 11:20:17 +0100

[eBay item #160698706252]

The listing reproduced (essentially stole) the ChromaFace section from the site. The listing ended apparently without a sale.

Chroma in Australia on eBay

Chris Ryan [21030691] · Sat, 24 Dec 2011 23:32:40 -0800

Item #260919010420, current bid AUD$1,510.00, five bids so far. Ends in just under 17 hours.

From the description: "For repair not for parts it's in beautiful condition and complete! This chroma has the updated power supply and cc+ with midi. unit powers up but displays error 01234567 on the display which means none of the voices are working and its outputting noise. When my friend connected the power supply a couple of connections were labelled incorrectly and nothing powered on but when changed it powers up. My tech tells me some chips on the channel mother board may be blown but I have no way of checking and being Xmas time nobody has time to go over it.

"This machine has been in storage for over 20 years From what I'm told as I purchased it from the USA early this year. Comes with sustain pedal, performance manual, photocopied interface manual and original flight case although the foam is in need of replacement (I will make sure it's packed well).

"Please note this is NOT working and sold as is, could be a minor fix or could be a major operation and in Australia there's only really a couple of guys that can or that I would trust to work on it so be prepared, but if you know the machine and or are up for the challenge then here's your chance to own an amazing machine. I did plan to wait and get it going but I already have another one that's working and another that's almost working and since ive spent a fortune to restore the others I really can't justify spending anymore on this one, you can only drive one Ferrari at a time.

"Hope it goes to a good home another working chroma in the world is a good thing and with all the support available it's one of the only vintage American poly synths worth owning in my opinion."

From the pictures I can't quite make out whether this is 21010150 (in the registry) or 21010158 (previously unknown); I've asked the seller.

Some of the pictures from the auction:

eBay260919010420a

eBay260919010420b

Luca Sasdelli [21010226] · Sun, 25 Dec 2011 09:58:50 +0100

"... a couple of connections were labelled incorrectly..."

I've tried to imagine the potential damages due to a PSU connector swap; this couldn't be used as a troubleshooting guide, but it could give a rough idea of what could happen in such as a case.

The PSU connectors are routed as follows:

  • J1: I/O board (analog)
  • J2: I/O board (digital)
  • J3: Channel Motherboard
  • J4: EQ board

Case J1 <-> J3

  • pin 1: ground instead of reset, so no fault
  • pin 2: +12V instead of +5V analog on Channel Motherboard & DVBs
  • pin 3: -12V to ground, so no fault (PSU protection)
  • pin 4: +12V instead of +5V analog on I/O board: some +5V devices received 220% over voltage
  • pin 5: +5V instead of -12V: inverted polarity on I/O board & CC+
  • pin 6: ground vs ground, so no fault

Case J1 <-> J2

  • pin 1: ground vs reset, so no fault
  • pin 2: +12V, -12V and +5V digital shortened together, so no both 12V
  • pin 3: ground to tapper, so no fault
  • pin 4: +5V analog to ground, so no fault (PSU protection)
  • pin 5: as per pin 2
  • pin 6: ground to tapper, so no fault

Case J2 <-> J3

  • pin 1: ground to ground, so no fault
  • pin 2: +12V instead of +5V digital to I/O board & CC+, but +12V shut down (see pin 4)
  • pin 3: -12V to tapper, so no fault
  • pin 4: +12V to ground, so no fault (PSU protection)
  • pin 5: same voltage so no fault
  • pin 6: tapper to ground, so no fault

I guess most of the connector swap failures should be related only to the I/O board, even if such as occurrences gives unpredictable issues; the last year I repaired a Chroma with most of Channel Motherboard chips (and DVBs logic ones) blown...

Chris Ryan [21030691] · Mon, 26 Dec 2011 14:35:24 -0800

Sold for AUD$2,625.00.

I/O board problems

Paulo Semprini · Mon, 26 Dec 2011 10:01:35 -0800

Hello-

I've been given a Chroma to work on, and while I've had a lot of experience on things like Prophet 5s and OB8s, I don't know too much about these -- would like to avoid mistakes if possible.

The unit has a new Luca power supply; when powered up, the front panel LEDs light and stay frozen (nothing in the number displays, except for one small segment of the data display).

Power to the two CPU chips is above 4.9 V; the chips both show data and address line activity.

My questions are: is this most likely a fault on the I/O board? -- if so, where's the most likely place to start? Also, could something else like the stack switch board or channel mother board be contributing? Is it possible to successfully power up without either or both of these connected?

I realize there are no easy answers, but I'd like to avoid doing the wrong things if at all possible. Any pointers in the right direction would be welcome.

Thanks.

Paul DeRocco [21030230] · Mon, 26 Dec 2011 10:15:43 -0800

If you get one digit lit up, the main CPU probably isn't running correctly. If you see activity on the data bus, it isn't being held in reset, but one thing that did sometimes happen with the old power supply is that it would put out a pulse train on -RESET which would never let the CPU get more than a few milliseconds into its program. I have no idea if Luca's power supply ever shows this symptom.

If -RESET is clean, you should investigate the CPU board first. Look for shorts on bus lines by looking for lines that sometimes show a value half way between a 0 and a 1, or two lines that look absolutely identical. I suppose it could also be an EPROM losing its data, which you could rule out by pulling them and reprogramming them with the hex files from the Rhodes Chroma site, if you have access to something that'll program 2716s.

Luca Sasdelli [21010226] · Mon, 26 Dec 2011 19:26:52 +0100

Il 26/12/2011 19:15, Paul D. DeRocco ha scritto:

If you see activity on the data bus, it isn't being held in reset, but one thing that did sometimes happen with the old power supply is that it would put out a pulse train on -RESET which would never let the CPU get more than a few milliseconds into its program. I have no idea if Luca's power supply ever shows this symptom.

Hi Paul and Paulo,

the PCB of SPSU kit simply holds the -RESET line low at boot for a few milliseconds and then releases it. The delay time was increased after some of the very first kits did cause a strange sustain pedal behaviour (it did operate the wrong way round just after a boot).

The symptom Paulo describes looks even to me as a CPU board problem or a generic data bus malfunction. Did the batteries lose some acid? Is the CPU PCB in good conditions or does it appear as contaminated? What if you press the RESET button on SPSU PCB? What if you disconnect P24 from I/O Board to the Channel Motheboard and then power it on?

Paulo Semprini · Mon, 26 Dec 2011 10:29:06 -0800

Thanks guys. Will check out all those things later today & let you know what happens.

Paulo Semprini · Mon, 26 Dec 2011 16:15:55 -0800

OK, found a faulty connector between the CPU & I/O boards -- replaced both connectors, and now it comes up. Am proceeding through the usual problems (voices won't tune, display segments missing, etc).

Had to replace the AD7541 to get the DAC trimmer to zero; reloaded the factory patches via cassette (since this unit is not recognizing the MIDI interface); keyboard & memory seem to be working, I now have to solve the not-tuning problem.

Thanks for all the helpful suggestions.

Go to next message in thread, March 2012

Question on the Poly Aftertouch / Pressure Sensor Kit Installation

Matrix [21030220] · Thu, 29 Dec 2011 17:40:29 -0800

I'm finally getting around to installing the Pressure Sensor Retrofit.

On the underside of the PCB there is a marker for middle C, however when I line mine up it's over middle B. Does this matter? One, I can't slide it over to make it middle C without drilling new holes in the damper bar, and two, if I did move it, the full strip would no longer overlap all the keys. I'm guessing I should just ignore the marker and go with what lines up with the keys, but I thought I'd check to be sure. If anyone knows, please let me know as soon as possible. I'd like to get it up and running for the weekend. I'll trying pinging Chris Borman [21030194+] off list as well.

Chris Borman [21030194+] · Thu, 29 Dec 2011 21:11:44 -0500

Make sure you read the online instructions and links to the comments from Jesper [21010135] and I. The sensor array is two identical boards, duplicate circuits on each side , one flipped over. The wood spacer hides the silkscreen you would see from a top view, or the proper mid c mark. Flipped over moves the mark one key down or the b.

A good idea gone bad...

Matrix [21030220] · Thu, 29 Dec 2011 18:53:39 -0800

Thank you for the quick reply Chris! Much appreciated.

I didn't get past "Power up the Chroma and check that the synthesizer is working OK."

I'll read the rest of the notes and report back when done. Wish me luck! :)

Matrix [21030220] · Thu, 29 Dec 2011 22:39:50 -0800

All done. The most challenging bit was definitely getting the vertical positioning just right. I ended up removing the green round felts underneath the keys and cleaned the keys while I was at it. I tested with and without the felts and couldn't quite tell the difference once I got things to my liking. I ended up leaving them off. Does anyone have an opinion on that?

See continuation of this discussion in March 2012

Also I forget if the Chroma will send poly aftertouch when this kit is coupled with the CC+ upgrade. Does anyone know?

Matrix [21030220] · Thu, 29 Dec 2011 22:51:22 -0800

There is one other thing I forgot to mention which I figured I'd send to the list as the answer might be useful to others. When sticking on the CPS sensor I ended up a couple of millimeters short on the left of the keyboard. It works just as well as the other keys, but is this something I need to worry about over time? In hind sight I should have had someone help me when applying it.

Another side note is I only had to remove two small connectors to be able to fully tilt back the front panel - one small connector on the modulation levers and one center left on the panel control board. I did have to snip a cable tie. That step wasn't as bad as I expected. I'd recommend carefully lifting the panel and giving all the wires an overview being careful not to pinch or snag anything. Most shifted away fine for me with the exception of the two connectors and cable tie.

Paul DeRocco [21030230] · Thu, 29 Dec 2011 22:58:36 -0800

All done. The most challenging bit was definitely getting the vertical positioning just right. I ended up removing the green round felts underneath the keys and cleaned the keys while I was at it. I tested with and without the felts and couldn't quite tell the difference once I got things to my liking. I ended up leaving them off. Does anyone have an opinion on that?

I liked it better that way, too. It makes the vertical alignment far less critical, because you're no longer trying to balance two independent key motion stops, one of which senses pressure and the other which doesn't.

David Clarke [21030085++] · Fri, 30 Dec 2011 09:03:15 -0500

... Also I forget if the Chroma will send poly aftertouch when this kit is coupled with the CC+ upgrade. Does anyone know?

Yes.

If you have CC+ with firmware version 213 or newer, you can transmit poly pressure. If you have 215 or newer, you can transmit poly pressure or channel pressure (user selectable).

To check the version of firmware you have:

[SET SPLIT 36][P25]

If firmware 215 is being used, ensure Polyphonic pressure mode is selected:

[SET SPLIT 36][P16] = Pol

To allow MIDI transmission of pressure, ensure that MIDI Pressure Tx is enabled:

[SET SPLIT 36][P26] = On

(Matrix - when your CC+ was originally shipped it had firmware version 214 installed - and so if you haven't updated to 215, the only step you'd need to perform to allow midi pressure transmission would be [SET SPLIT 36][P26] = On)

David Clarke [21030085++] · Fri, 30 Dec 2011 15:45:24 -0500

Threshold Pressure

... I was wondering how to get channel pressure working as well. It looks like I need to upgrade...

All versions of the CC+ will receive Channel Pressure - but if you want to transmit Channel Pressure (from the keyboard), then a firmware upgrade is the way to have that option.

In my editor I have Threshold Pressure and Pressure as modulations sources:... Is one poly vs channel, or are they referring to something else?

They're not specifically referring to poly vs. channel (per se) but instead they allow the pressure data to directly modulate program items.

The Chroma keyboard fundamentally deals with 'poly' pressure, as it will allow a different pressure value for each and every key. If you are triggering the sounds from the Chroma - then the 'pressure' will be treated internally as poly.

The Chroma can receive Channel Pressure - but it doesn't actually have a native way to use it as 'pressure', so just like the KMX interface incoming Channel Pressure messages are converted into pedal 2 commands.

If you want to 'play' pressure into a sequencer, and then have the sequence played back to the Chroma and get the benefit of pressure modulation sources, you will want to use the native Chroma pressure mode (Poly).

In terms of the two settings noted, the 'pressure' modulation source is just like 'velocity' in that it is a user-controllable value that can be used to modulate a patch parameter.

"Threshold Pressure" is a bit different.

You'd instinctively expect it to work like the 'Attack' and 'Release' thresholds whereby you can set a threshold value (with [SET SPLIT][21]/[SET SPLIT][22]) but you'll not see a specific [SET SPLIT] configuration for the Pressure Threshold.

(To be honest, I never really thought about this or noticed this before.)

Instead, the 'Threshold Pressure' mod source implementation the original Chroma firmware (and as carried over into the CC+ code) works sort of like a binary switch, or at least a 'low pressure cutoff'.

If the pressure asserted is less than half of the full value, then the pressure mod amount is "0" (e.g., pressure modulation is being done - but as if the pressure is '0'). If the pressure asserted is more than half of the full value, then pressure modulation is performed, with the 'pressure value' being half of what pressure would normally be pressed.

Matrix [21030220] · Fri, 30 Dec 2011 09:19:38 -0800

Re: Threshold Pressure

That is awesome. Thanks David. I was wondering how to get channel pressure working as well. It looks like I need to upgrade. In my editor I have Threshold Pressure and Pressure as modulations sources.

Is one poly vs channel, or are they referring to something else?

Matrix [21030220] · Fri, 30 Dec 2011 19:24:57 -0800

Re: Threshold Pressure

Thanks David. Is there a way to play channel aftertouch exclusively on the Chroma so that if I apply aftertouch to one note it's applied to all locally? Not to control external synths but to control the Chroma itself. I'm finding that not all my fingers have equal strength so I'm getting varying levels of aftertouch for each note. :)

David Clarke [21030085++] · Fri, 30 Dec 2011 22:41:13 -0500

Re: Threshold Pressure

As the Chroma natively handles per-key pressure, I'm not aware that the Chroma itself has a direct capability to do this - but I'll certainly bow to others on the list who might have an idea how that can be done.

The only way that comes to mind would be to perhaps set up the Chroma to have Channel Pressure selected for transmission via MIDI - and then set up the Chroma with Local off. In that way, the Chroma won't 'play' the native poly pressure - but instead sends channel pressure via MIDI - and then would receive it back by an external MIDI device sending it back to the keyboard. You'd then have to set up the controls so that the effect you wanted was implemented with a "Pedal 2" controller (as that's how the Chroma will handle the received channel pressure messages).

Chris Smalt [21010280+] · Sat, 31 Dec 2011 05:00:22 +0100

Re: Threshold Pressure

I'm finding that not all my fingers have equal strength so I'm getting varying levels of aftertouch for each note. :)

Coupla years practice and you're good... ;-)

Go to next message in thread, January 2012

Chroma in Spain on eBay

Chris Ryan [21030691] · Thu, 29 Dec 2011 22:59:16 -0800

Item #120835786585, starting bid USD$4,995.00, no bids yet, buy it for $6,000.00. No picture other than the centre spread from the product brochure and not much info posted: "Revised by MJ in LA [not sure who this might be], in excellent condition, comes with pedals, JL Cooper Chromaface w/ribbon cable (midi interface), and ATA flightcase." I've asked for more details.

Chris Smalt [21010280+] · Sat, 31 Dec 2011 04:22:33 +0100

"Revised by MJ in LA [not sure who this might be]

[Warning: end of year humor]

Helpful advice for finding MJ in LA can be found here.

Go to next message in thread, January 2012