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ChromaTalk Archives: July 2005

Building/Replacing Chroma Voice Cards

David Clarke [21030085++]

Ever wanted a cleaner voice card schematic? Ever needed to repair your voice cards? Ever needed to replace a voice card? Ever wanted to build additional cards for your own Chroma project?

Well - additional information to help is the subject of July's Rhodes Chroma site addition: Building New Voice Boards.

Chroma + Berhinger BCR2000 can't save the sounds

Danny Wolfers [21030921]


I am the owner of Rhodes Chroma with the Chroma Cult interface, I've bought a Behringer BCR2000 MIDI controller to control it, this works perfectly...but:

When I save the sound it doesn't save any changes made with the Behringer...the changes seem to be discarded and I have the original sound I started with.

Why doesn't it save the changes?

What can I do about this?

David Clarke [21030085++]

Danny - I hadn't really thought about this before - but my best guess is that the behaviour has to do with how 'instruments' and 'programs' are managed on the Chroma and what the MIDI interface does with them.

Specifically - at any one time, the Chroma can have up to 8 instruments defined (numbered 0->7).

The Chroma midi interface can be configured to use a certain number of these (up to 8).

Generally the way it works is that the intruments are assigned based on the assigned midi channel.

For instance, if the midi interface is set up to use 3 channels/instruments - and if the base channel is "9", then we'd have:

  • midi channel 9 -> chroma instrument 0
  • midi channel 10 -> chroma instrument 1
  • midi channel 11 -> chroma instrument 2

Each Chroma instrument can respond to controllers - so if you send in controller data in on channel 10 - and you'll successfully affect instrument 1. Similarly, you can send in controller data on channel 11 and you'd affect instrument 2.

Inside the Chroma, Instruments are defined by passing in a program number.

When you do a MIDI patch change (let's say we change to patch 12 on Midi Channel 10, in this example), then the chroma does a "define instrument 1, based on program 12."

From this point on, any commands coming in on instrument 1 (channel 10) will be modifying a copy of the program 12 data.

The reason that this explanation is important is that the front panel controls only affect 'program 0'.

For instance, when you press a program button on the front panel, inside the chroma it creates a new instrument based on the program. That instrument is referenced to patch/program 0 (the working patch).

Any chroma panel changes from that point on are made to 'program 0' - the active program.

Keeping this in mind, if you use the BCR2000 to send a continuous controller to the Chroma (to change a parameter), then the parameter change will on a certain midi channel. That channel is associated with a particular instrument, and that instrument is defined by a copy of a program.

Carrying on with the example above, if you sent a continuous controller message on channel 10 - then you'd be affecting a copy of program 12.

The only way that you could have the external continuous controller data affect the panel/current/working program (i.e., the one you can save with the panel buttons) would be if you could somehow have the instrument reference program 0.

Unfortunately, the Chroma Midi Converter doesn't allow you to do this. If you attempt to send a "MIDI patch change" and pass in patch number 0 the Midi Converter would perform an 'undefine' operation on the instrument (per the Midi Converter manual) instead of passing this on to the Chroma directly.

In summary, it does not appear that you'll be able to easily 'save' a program that has been 'changed' with an external MIDI interface; rather, the best/easiest way to do this is to leave the original patch unchanged, and 'snapshot' the controller settings into a sequencer (so the changes are reapplied each time you want them).

To make the settings more permanent, you'd could do so via a manual edit (i.e., snapshot the changes, and then manually update those handful of controllers via the front panel interface of the Chroma).

A slightly longer-term way to fix this behaviour would be to edit the firmware inside the Midi Interface to handle the continuous controller/instrument definition messages differently.

Danny Wolfers [21030921]

Thank you very much!

Danny Wolfers [21030921]

Another question regarding the chroma:

Upon starting up and after the testing the Chroma LED sais "ERR 6".

What does this mean?

David Clarke [21030085++]

Meaning of "ERR 6"

Danny - this generally means that the 6th voice-card has failed 'autotune' when starting up.

Some additional information is available in the FAQ.

Look for the "What does 'Err 012' (or the like) mean?" entry.

Chris Ryan [21030691]

This is in the FAQ. See "Error Messages" in the Diagnostics section of the Performance Manual.

Chroma on Analogue Heaven

Chris Ryan [21030691]

From Analogue Heaven:

Date: Sat, 2 Jul 2005 17:42:34 -0700 (PDT)
To: Analogue Heaven
From: Doug Terrebonne <>
Subject: SF Bay Area Moving Sale - Tons of Stuff!

Hi, I plan on moving to a smaller place soon so I have the following for local sales -

$750 Rhodes Chroma

This is Chroma 21030401, previously advertised in August 2004 at a slightly higher price.

Voice Card Repair

See first message in thread (June 2005).

David Clarke [21030085++]

I recently acquired a Rhodes Chroma S/N 21030674 and am glad to have joined and be part of this group.


I currently have a problem with 1 voice card constantly failing autotune ... Is there anyone on here who can kindly help in the repair, troubleshoot or service voice cards ...

The voice cards are generally not too difficult to diagnose and repair (especially for those cards that very sick).

A good staring place would be the contacts from the 'Service' page from the Rhodes Chroma web site at:

Edward Chen [21030674]

Hi Dave! Thanks for the response as I shot an email to John [21030434++] at Cantos and am awaiting his response as to whether he still repairs/service voice cards w/o the need for me to ship the whole unit. I will keep you guys posted on my Chroma restoration.

Edward Chen [21030674]

Hi Dave,

Just giving you a follow up as JL from Cantos contacted me back and was more than happy and kind enough to service my 'bad' voice board. His rate is $70CDN per hour which is fine for me since I would not have to ship the whole Chroma to him just the 'bad' voice board. He told me he still stocks everything that usually goes wrong with it.

Thanks again for your suggestion and referral!

Keys not responding?

Christian Kleine [21030210]

Hi list,

I just joined this list today (after purchasing my Chroma two days ago). The serial is: 21030210

It once belonged to David Morley, he sold it to a person in Cologne and I bought it from Cologne. I rented a car, picked it up and brought it to its new home in Frankfurt.

The Chroma is a truly wonderful instrument! I have the Anvil case, the Chromaface as connector but i need to buy a power supply for it.

My Chroma works fine so far, no faulty voice boards but: 4-5 Keys don't respond. Some give a tone after hitting them quite fast, other ones don't respond at all.

Can someone give me a hint on this problem?

Chris Ryan [21030691]

I just joined this list today (after purchasing my Chroma two days ago).

Welcome to the list!

The Chroma is a truly wonderful instrument! I have the Anvil case, the Chromaface as connector but i need to buy a power supply for it.

For the ChromaFace? I'd recommend picking up a Syntech/Chroma Cult MIDI interface instead. It's the standard interface, is much more capable, and is required for many software packages.

My Chroma works fine so far, no faulty voice boards but: 4-5 Keys don't respond. Some give a tone after hitting them quite fast, other ones don't respond at all. Can someone give me a hint on this problem?

Try cleaning the key contacts.

Olli [21010284]

maybe try playing with the key contacts, cleaning if that doesn't help bending the upper contact down very little.

David Clarke [21030085++]

christian kleine wrote:

...I have the Anvil case, the Chromaface as connector but i *** *need to buy a power supply for it. ***

A replacement power supply should be quite easy to find (from a local store); however, if you run into troubles (and if you don't mind using a solder iron), it is a quite easy modification to have the Chromaface automatically get its power from the cable that comes from the Chroma.

... *4-5 Keys don't respond.

I second the advice already given on the list. Specifically, 95% of key problems will be fixed either by removing the dirt/debris between the contacts, slightly re-adjusting any out of place contacts and/or ensuring that the damper bar isn't adjusted too lowly (preventing the contacts from being open far enought). Open the lid of the Chroma and watch the key contacts while you're trying to make them sound.

With regard to the last point, the service manual provides guidance as to how to ensure that the damper bar is appropriately adjusted.

We're glad you found us. Welcome to the list.

Fwd: Bob Moog

Vincent Russo [21030433]

I do not think many of us would be into synths if it wasnt for Dr. Moog, so i hope this is on topic.

Guys, hate to report Dr. Moog is undergoing treatment for a brain tumor. You read his blog or leave him a greeting in his guestbook [both gone by 2009.07].

Jesper Ödemark [21010135]

I heard this on another list, but apparently they want to keep it apart from the business of Moog music though I heard they confirmed it...

Chroma on eBay

Chris Ryan [21030691]

Item 7336457691.

Syntech/Chroma Cult MIDI, minor foam damage, US$500, reserve not met, ends July 19.

A couple of the pictures:

Fwd: Chroma on Ebay

Chris Ryan [21030691]

A "Rhodes Chrome" for sale! Working condition unkown; some foam rot. No reserve.

From: Edward Chen [21030674]
Date: July 24, 2005 9:32:07 PM PDT
Subject: Chroma on Ebay

Hi Chris,
Came across a Rhodes Chroma FS listing on Ebay. Wouldn't have known being the seller spelled it incorrectly. Thought this may be of interest to someone on the board.

[Item 7338600251]


This is Chroma 21030765. Pictures from the auction:

Jesper Ödemark [21010135]

Looks like it's in a nice condition cosmetically... Someone in the area ought to pick it up, 200 is nothing!

Doug Terrebonne [21030114]

Looks to me like the only pict of the actual unit is the one of it inside the case... Also since its not working I would be very cautious speaking from personal experience with one that had battery leak damage to most of the chips on the CPU board... Also I tried using his shipping calculator and it told me the item could not be shipped to me even though I'm also in Calif!

Paul Hackett-Evans [21010094]

It looks to me as if the two photos of the beautiful, clean shiny Chroma are of a different machine than the dirty, foam-rot encrusted one in the flightcase. The seller probably wants to show a perfect example to give potential buyers the idea that the Chroma is a nice synth. Then the flightcased pic is to show what you'd actually be buying.

Still, if it were cheap and near to you, you'd want to consider it as a restoration project.....

Edward Chen [21030674]

Yes the 2 nice photos were C&P from the bluesynth site [see Reviews for the current URL].

Jesper Ödemark [21010135]

Hi list!

I just read Dave's efforts at making new Chroma boards - interesting. But I still hope someone gets the unit on Ebay 'cause if just a few IC's are OK in that one it would be a bargain as spares machine...

Or let me say like this - if it was in Sweden, or even Europe for that matter, I would buy it!

slightly-OT: case padding rot

Jesper Ödemark [21010135]

we chroma owners often complain about crappy padding. Check this poor Oberheim for a worse example.

eBay Item 7338595004; here are a couple of the pictures:

Can't someone in the Indiana area save the poor bastard. I bet it's "just" battery and some dry soldering...

Chroma display

Tom Moravansky [21030431]

Quick question for the list:

Over the years the Chroma UI has gotten a lot of flack and some solutions have been proposed (including a really cool knob box).

However, has anyone ever looked into a simpler solution?

What I was thinking of was simply a 20x2 or 40x2 LCD display that showed some helpful text as you pushed a panel button and scrolled through the values with the slider. Basically take the text from the cheat sheet that everyone has and display it.

Would something like that be easier to do than a full-blown knob box?

David Clarke [21030085++]

Something like this wouldn't be terribly hard to do for anyone that likes to do some hardware work.

Perhaps the easiest method to do this would be to create a little interface to listen to the Chroma Port (DB-25), and then just decode and display the data seen (all of the parameter/value data is available on the port - you just have to add in the 'decode' portion, and add the text from the cheat sheet.)

A small PIC chip could likely be programmed to interface with the Chroma Port and the LCD display of your choice.

Alternatively, Sandro's Chroma Expansion Board could be used as a replacement CPU board - giving more program data and control to the user - (and a custom display interface could be hooked into that, keeping the Chroma Port free for other tasks).

Yet another idea would be use Sandro's board without modification - and to have it send MIDI cc's for all parameters. With that setup, a small MIDI decoder could be set up (either via custom HW, or via an application running on a PC) which would decode the MIDI data, and show the parameter text.