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ChromaTalk Archives: March 2007

Keyboard Spec Sheets

Chris Ryan [21030691]

This month I've added a couple of short articles from Keyboard magazine, April 1982 and March 1983, announcing the Chroma ("Rhodes Synthesizer") and Chroma-Apple Interface.

chroma reverse

Fredo Fraile [21040011+]

Hello, can someone tell me why my chroma keyboard works in a Zawinul style, means the highest note is on the bottom and deepest on the top [see Zawinul's endorsement in Magazine Advertisements], I can not find any information about changing that,thanks for help (this is the second Chroma I bought, because the first one is still not working, it was the Chroma from Sweden,this one has also a problem with one card and the psu, but it works sometimes serial number is 21030593 I bought it from stefan kraft gelsenkirchen -buer germany send a picture later).

Jesper Ödemark [21010135]

Maybe it is the Zawinul one! :-o

Fredo Fraile [21040011+]

hi, nice joke, but i do not think so, because it first worked normal, i think it depends on my low knowledge about the chromas possibilities seems that it happend by accident, so you do not how to change it?

Jesper Ödemark [21010135]


Is it in tune, then? It sure sounds like the keyboard scanning circuit has gone haywire... :(

Fredo Fraile [21040011+]

do not make me nervous, i think it is programmble, the chroma needs some time to get in tune, he has a problem with the old psu, but i think that is not the reason, it must a have reverse function or not? however i bring it to repair next week, and after repair i will see if it has the same behavior as before, thought someone outside there knew a trick to reverse it again.

Jesper Ödemark [21010135]

Wait for David, Sandro or Chris to awake and I bet they have an easy answer. There probably is some "switch operation" but I'm not familiar with any. I use mine in the normal fashion. ;)

Fredo Fraile [21040011+]

that's what i also want to do, thanks, i wrote about your knobbox, was that right? do you build by yourself? i also would like to have one, my second chroma has a syntech midi, do you know if it is possible to use one of this modern knob, or sliderboxes like behringer or so to use with this midi-interface?

Jesper Ödemark [21010135]

Hi Fredo!

No, the knob boxes available all uses CC messages and the normal midi versions of the Chroma doesn't support this. But if you upgrade the Chroma with David's and Sandro's magnificent CC+ it will accept CC messages. I've only just briefly tested mine with a Doepfer Pocket Dial but it works like a charm! Now I can't wait to lay my hands on a Doepfer Drehbank instead to get even more knobs for _everything_!

*insert mad scientist laughter here* ;)

Fredo Fraile [21040011+]

Hi Jesper,thanks for that information, sounds good, but the do not have the CC+ on stock? I would like to do this on my first chroma, from sweden.

Dave Bradley [16330135]

You can make it do this with a programming trick by applying negative pitch mod using the keyboard as the source. There was a factory patch that used this.

If you are saying that all your presets do this, that's weird.

Fredo Fraile [21040011+]

Hi, i do not have the factory sounds, my chroma sometimes forget everything after turning power on, so this happens with a scratch sound after he forgot everything and i tried to programm new sounds, i own this machine only a couple of days and i am not totally familiar with it.

Fredo Fraile [21040011+]

Hi, i looked at the chroma site joe zawinul's advertisment for the chroma that the chroma has this fucntion the mirror key, so it is not a malfunction, it must be a hidden function, which i used by accident.

Dave Bradley [16330135]

Go zero out all the modulations for Pitch.

David Clarke [21030085++]

Using MIDI CC for knob control

No, the knob boxes available all uses CC messages and the normal midi versions of the Chroma doesn't support this. But if you upgrade the Chroma with David's and Sandro's magnificent CC+ it will accept CC messages.

Just a slight clarification on Jesper's earlier reply. It is certainly true that the CC+ can be used to support of external knob use (e.g., through the use of MIDI CC or SYSEX) but the Syntech interface does also offer a specific, limited set of CC messages too.

That means, if you are only interested in controlling the parameters documented in the Syntech manual, then you should be able to successfully do this via an external slider-box. So, if you already have a Syntech MIDI interface, you would be able to implement some external control.

The CC+ offers further capabilities in that it allows all of the Chroma's parameters to be accessed via MIDI CC (not just a subset), and also allows access to the parameters via SYSEX (for controllers that may not directly support MIDI CC).

rockets and chroma

Jesper Ödemark [21010135]

Here I'm sitting watching videos I've never seen before with one of my favourite bands; french synth-discoband Rockets. And what do I see if not a Chroma with an ENORMOUS logo on the back - were they sponsored???

It says it's from 82 so it might have been a step in the launch maybe?

Dave Bradley [16330135]

Wow. Weird band, weird Chroma. I kinda liked the song though.

Ron Joseph [21030042+]

What's the synth on the top? Chroma. Jup-8, ???.

Matrix [21030220]

Prophet 5 I believe.

Werner Schöenenberger [21010114]

Yes, but they also used a lot of PPG - so I miss that one ;-)

Jesper Ödemark [21010135]

I have a lousy guess at a RSF but I'm not sure...

Martin Pavlas [21030450]

prophet 5 with removed name plate I would say...

Totte K [21010104]

band in tights haha that singer is bit too much...but yesh their keyboardist is real synthhead. He has seen that only proper way to approach his mighty Chroma-Jupiter-Prophet rack is... movin fiercely in pantyhose. He aint even playing the chroma only can hear it for some 3 secs. and then that riduculous guitar againg. what a waste.

Jack Colburne [21030142+]

Very cool video. Made me (almost) feel young again. :-)

But, they're lip-synching, so the sounds on the recording aren't necessarily (or likely to be, for that matter) the keyboards that he's "playing live" at any given moment anyway. I bet alot of it is the PPG mentioned by Werner. And no-one's playing the carrier signal synth for the lead singer's vocoder.

(Unless the lead singer had some very extreme surgery to alter his voice) ;-)

Paul Hackett-Evans [21010094]

"But, they're lip-synching, ..."

It looks as if none of the keyboards are plugged in! ... .and why are the band members all wearing silver nappies? (diapers for our American members!)

Really, though, what a great band - they really look like a fun bunch of guys!

Jesper Ödemark [21010135]

OK, mystery solved - thanks! I should've guessed since they have a P5 on the inner sleeve of "Atomic" released at that time...

Werner Schöenenberger [21010114]

Yes, I know by an information from a friend that they used a PPG Wave 2.0 - other story ;-)

Bad Voice Problem

Werner Schöenenberger [21010114]

Hi list,

the new CC+ board arrived last week (thank you so much, Sandro) and before replacing the board, I intend to fix the bad voice my Chroma currently has. A small step - I thought... But unfortunately I do not have success until now. Maybe somebody can help

I did the following procedures:

  • displace the board, to verify that that the issue is located on the board -> it is
  • replace the 4051s and 4556 without success -> no S&H issue
  • measure at VCO out and VCF out -> wonderful square signal
  • test with <SetSplit> 31 -> Voice A is detuned by about 1/2 semitone, Voice B is detuned by about one semitone
  • test the Filter resonance -> everything ok

Since the issue happens on both voice, my current idea is a problem with the TL082 because this affects both voices (I currently do not have one in stock). Does anybody have a hint? Everything is appreciated. Thank you in advance.

BTW: When opening the Chroma, I noticed the S/N: 21010114 - Chris, I will you send additional information when having fixed the issue.

Werner Schöenenberger [21010114]

Oh, I missed something: of course, I checked the +5 Voltage and the DAC....

Sandro Sfregola [21010294]

Werner, before doing anything else I suggest trying the following:

  • adjust the 5 Volt analog supply to 5.05 Volt
  • do the charge pump trim procedure described in the service manual
  • pull the defective voice board from the Chroma and measure (with a good multimeter) the actual values of 1.87K TC resistors R3, R4, R5 and R6, then let me know these numbers.

Robert Kastler [21030157]

Hi Werner,

Sorry for being of no help, but I'm in a pretty similar situation - installed the fantastic CC+ (works like a charm - thanks Sandro, again) but have one bad board. So I just wanted to ask where you got the 4051s and 4556 from ?

I'm not that experienced technically but thought I would be able to replace the ones if I knew where to buy ...

Werner Schöenenberger [21010114]

Hallo Sandro,

the 5 Volt, charge pump and DAC was correct. In the mean time, I found the issue - as usual in my Chroma, somehow special and not easy to find - I replaced the complete frequency control part (even the transistor array) without success. But the story might be something for the archive.

The issue was in the 4052, that drives the output lines of the voice board. Somehow it was half dead so that the output was routed to sum #2 instead of sum #0. This means that the selection lines of the dual 4 channel analogue switch did not work anymore. So the Zero Cross Detector (ZCD) was not addressed during the tuning cycle and the tuning failed. The strange thing was that due to the fact that the output worked and was directed to sum #2, <setsplit> <31> routed all voices to the main out and this made the impression that the output module works proper.

How did I finally identify the issue: I connected a scope to the TP1 of the defect board as well as a second channel to the TP1 of a working board. When comparing the signals, I saw that the defect board only was scanned by the tuning cycle once (high frequency of the square signal) whereas the working board was scanned twice with keeping the signal at high frequency for the third scan. So I first thought that the issue was in the s&h circuit and I replaced the 4051 and 4556 again (without success). So I checked the schematics again and saw that the ZCD only works on sum #0. By plug in a jack in the audio in/out socket at the back of the Chroma, which disables the sum #0 at the mono out, I noticed that only the bad voices sound in debug mode (<setsplit> <31>). After that it was easy to figure out that the voices always were routed to sum #2 and my first trial to exchange the 4052 (IC # Z17) brought the success. Hallelujah :-)

So, I just have to save now my current sounds and then I will start to build in your board...

Werner Schöenenberger [21010114]

Hi Robert,

you can get these components in all good electronic shops. Just try e.g. and enter the fast search 4051 - and here we are. You also can buy there any sockets for the ICs which makes replacement easier in the future.

Robert Kastler [21030157]

Hi Werner,

Thanks for your help - did not think it would be that easy ;-))

... and I'm glad to hear that you have solved your problem (obwohl ich Deiner detaillierten Schilderung ja nicht wirklich folgen konnte .... hope it's not getting that complicated for me ...)

Anyway, thanks again - I will let you know if I can cure my board ...

Jesper Ödemark [21010135]

you can get these components in all good electronic shops. Just try e.g. and enter the fast search 4051 - and here we are. You also can buy there any sockets for the ICs which makes replacement easier in the future.

I can only second the last comment. Do socket all ICs when you replace them. I do this with even the cheapest and crappiest ICs around so I or someone else won't have to swear a lot to remove the IC next time.

windows interface

Dave Bradley [16330135]

Go to first message in thread, November 2006

Did Mark ever send his editor source code?

Chris Ryan [21030691]

I asked him a couple of weeks ago. He believes that it is on a laptop hard drive he has, though he no longer has the laptop, so needs to buy an external drive bay.

Mark's work was later posted in its entirety: see A Windows Interface for the Rhodes Chroma.


Krisnallah Sumy [21010282+]


I have tried to load a factory syx into my Logicaudio- window xp it doesn't seems to recognize the file extension SYX, I did not try it in my Cubase sx 3 because it is 4 in the morning need sleep to energize I wonder if EES has a dump prg that recognizes .SYX Can one tell witch program to use this sys excl to dump the patches

David Clarke [21030085++]

The .syx extension is not always used or expected by programs. If LogicAudio (or other programs you have) have the ability to load a 'binary sysex' file, then they should be able to read the .syx file. You may need to specifically tell the program to 'load sysex', and then point to he file (vs. having the program automatically associate .syx with the function).

Sandro Sfregola [21010294]

Sumy, I can confirm that you will be surely able to upload sysex files to the Chroma using Cubase SX 3 (tested) and a suitable MIDI interface (M-Audio for example).

Halloween/Red Membrane Panels

Chris Ryan [21030691]

Greg Hutchings of Hutchings Keyboards in Australia (who seems to have sold many, if not all, of the [known] Australian model 2104 Chromas) e-mailed me some pictures of replacement membrane panels he recently came across. This is one of a small number of obscure "Red" or "Halloween" themed instruments or parts; see also Chroma 21030620 and More Halloween Chromas (October 2001).

Jesper Ödemark [21010135]

Cool to see such a rare spare part. Sad it won't fit on a standard chroma 'cause I'd love to get that colour on mine... :)

David Clarke [21030085++]

Chris - any indications as to what the intended fate of the replacement panel will be? (i.e., does he intend to keep it, put for sale on the Chroma site, etc?)

Chris Ryan [21030691]

He's planning to use it in restoring one of his Chromas; he found another and is going to use it on his Expander.

Jesper Ödemark [21010135]

Good that it's getting used... I mailed him as soon as I saw your post and asked if they were for sale! :) No answer though...

electronically yours, jesper - who simply loves the look of the autumn/halloween Chroma

CC+ Board

Werner Schöenenberger [21010114]

Hi list,

I installed the CC+ board today. Fact is, that

  • it arrived in perfect and professional package
  • it is manufactured professional
  • it is easy to install (perfect installation description)
  • it works plug-and-play
  • it is GIANT fun

Sandro & David - you did an indescribable and professional job - I know, it was done during your spare time. I only can recommend do everybody who did not already, to invest into this exciting board. In my studio, it will make my Chroma to be fully integrated into my MIDI setup.


Robert Kastler [21030157]

Hello everybody,

Having installed CC+ last week into my perfectly dead (bad cassette - , JL Cooper MIDI - interface, memory loss) Chroma, I can only double Werner's most accurate evaluation of CC+.

Special regards to Sandro & David & all

Jesper Ödemark [21010135]

So now it's alive and kicking? Cool!

Olli [21010284]

hi i got mine yesterday after my return back from holidays. package great, looks very well built, havn't installed it yet. thanks guys

Robert Kastler [21030157]

Yes, I'm really happy ...

And my (otherwhere mentioned) voice board problem finally turned out to be a simple contact interruption - since I changed places of voice boards 2 resp. 3 the error is gone ... Yipppiiee. ...

Thanks for your interest and best regards to all

Jesper Ödemark [21010135]

Congrat's! =)

Another working Chroma...

looking for a chroma


Hi, I've owned a Chroma when they just came out, but sold it later (unfortunately ;-)

Now I am looking for a Chroma again - so if anyone would like to sell one (or an expander) or knows about one which is to sell, please let me know.

Tom Klepacki [21030025]

Hi Laurin,

I am flirting with selling my Chroma #25. Yes, one of the first ones... She needs to be taken out once in a while, and played with... and repaired/ restored. I bought it new in 1982. I even have the cassette 'fast and slow' program dumps, dated June 17, 1982, and all other accessories. I still haven't made up my mind, for sure... Contact me, via email?

Mike Jaynes [21030638+]

There is this one on SF craiglist.

URL removed. Text from ad: "Fender Rhodes Chroma analog synthesizer in fantastic condition. All wood has been replaced with new curly maple and it looks and sounds great. One of the few that was made by ARP and has ARP cards in it. Serial #0012." The seller confirmed that it is 21030012. Previously for sale in February: see Chroma on Craigslist.

I emailed the owner, he wanted $2500, but I do not know him or if it even still available. It is located in Modesto in the California central valley. He said in his email that it was in excellent condition. Might be worth a look.

David Clarke [21030085++]

Laurin - there's also one listed on the 'Ads' page from the Chroma site.

Jesper Ödemark [21010135]

ARP cards, #12 and vents on top... Wasn't all these released without the vents or am I hallucinating?


Hi Tom,

do you have some pictures from your chroma, which I can see?

What is wrong with it? And if you decide to sell, how much will you get for it?


Hi David, thanks for your tip - I didnt know this list. But the selling ad is from 2003 - but however I will send a mail and try it.

Chris Ryan [21030691]

As far as I know, this instrument is still for sale. I check on the ads periodically to confirm they're still active.

Chris Ryan [21030691]

There is this one on SF craiglist.

This listing is now deleted, but the seller let me know that it is serial number 21030012, the earliest model 2103 we now have in the registry.

Jesper Ödemark [21010135]


I surfed the site and registry a few hours ago (in the middle of the night) and was surprised how many high number 2101's there are. There are entire complete sequences here and there. I think the Chroma registry is great since it comes with those nice little stories unlike for example "lords of the mini" which simply adds the serials...

CC board acid damage repair info

Chris Ryan [21030691]

I received the following troubleshooting and repair information from Brian Marshall, owner of Chroma 21010108.

Begin forwarded message:

It has been out of use for the past 18 months and I began a new project 3 weeks ago. I turned it on and all the LED's came on together without any boot up flashing of the board interrogation and tuning. Sometimes in the past it would stick occasionally after some of the sound boards had been verified but it had never done this before. I tried all the usual things but turned to your site for advice. I discovered that leaking batteries from your discussion forum might be worth a look as i hadn't changed them for years. Sure enough, they had leaked on the Computer Board. It didn't look too bad so I cleaned up the board, replaced the batteries and refitted the board but the problem was still there - all the LED's came on and nothing else happened. I looked again at the site and decided to look at the power supply as this seemed to be the first and most obvious thing to check from what others were saying, but I wasn't sure in myself that this was the problem. Anyway, I checked the voltages - digital +5v was reading 5.05v on the PSU and just over 5v on the I/O board as per the site. The 5v analogue was at 5v but the +/-12v was odd in that the reading was +9.65v and -9.65 volts. I checked out the schematics of the PSU and thought that the problem must be in the +12v generator because the +/- volts were reading exactely opposite, so the -12v generator must have been ok, being fed by the +12v that was generated by the +5v analogue generator (which was also ok).

In despair I eventually rechecked the Computer Board board again for possible signs of acid damage. After a reclean with a soft toothbrush and a more indepth examination with a good magnifying glass I noticed what might be a break in the solder track on pin 15 of Z7 address IC on the top side of the board, but as the solder track was so small it wasn't easy to tell if the track was connected to pin 15 of Z7 as it is only about 5mm long. (see circled below) This connection went through the board and joined up with pin 5 of address IC Z6 on the other end of the board. I checked back on the board layout and schematic in the site and confirmed that the connection was true. So using just one thin strand of fine copper wire about 5mm long, I soldered it to the underside of the board at pin 15 IC Z7 and the other side of the through board track. This problem may have been overlooked by those suffering with acid leak as this corroded solder track appears to be one of the thinest and smallest on the board and it happens to be located near to the batteries. It sits next to the other possibly smallest track on the board but even looking at the drawing below (from the site) the track in question is easy to see as being half the size of the one on pin 14. I never noticed it on first examination as the green layer on the solder track was hiding the problem and it was probably only after a thorough cleaning with a toothbrush that removed the top layer that I was able to just about notice it with the magnifying glass, though my first thought was that the toothbrush scrubbing had caused the break and that it may have been intact before coming into contact with the brush.

Not believing that this would solve the boot up problem as it seemed that the +12v generator was at fault I reconnected and turned on and incredibly - it all worked!!! It all booted up and flashed as it should. I checked the +/- 12v lines again and they were restored to exactly +/-12v ... ?

All the programs were there, but only in parameter settings, not in sound. I tried resetting some of the parameters with set split and pressing each parameter in turn but no luck individually, when done in blocks starting at 1 to5, 6 to 10 the sound appeared but not relating to a specific program previously created. However, everything was working to a fashion which was great. After reloading sounds and connecting the midi box everything is working perfectly again. I hope this may be of some help to others.

MIDI Controllers

Andrew Dalebrook [21010180]

So I finally got around to plugging in my Behringer BCR-2000 (a MIDI knob box) through the KMX interface, and it learns the functions (CC messages) easily enough. There is a problem, however. Because each CC edits one parameter on one voice (A or B) only, you would effectively have to edit each parameter twice, one for the A voice, one for the B. Whereas editing both parameters on the Chroma directly is accomplished by pressing both "Edit A" and "Edit B" simultaneously.

Is there a certain trick to merge CCs together, perhaps in software? Or could this be an addition to the CC+ soft/firmware?

Go to next message in thread, April 2007

Chroma # 0012 up on the bay

Ron Joseph [21030042+]

Under Ebay U.S., synth section. Someone, I think the seller, was posting this on the S.F. craigslist [see looking for a chroma above]. I guess he decided to sell it on the bay. Oddly, he has 2 different Chromas pictured on the ad. One has all white keys and vents on the top, the other is one of the ivory keyed w/ exclamation point white key at the top "g" I emailed for clarification as to which prefix 210x his Chroma was and also why he had 2 different Chromas pictured. Hope it goes to a good home.

Chris Ryan [21030691]

This is eBay item number 200092339576. There appears to be a bid for US$2495; is that a real bid?

21030012 is in the registry.

Jimmy Moyer [21030184]

$3450 now. (!?!)

Ron Joseph [21030042+]

Wow, that's high. There are two bidders who obviously really want this. I've corresponded w/ the seller and don't think its foul play on his part. First fifty collectible aspect? Who knows....tempts me to sell one of mine though.

He's selling a bunch of gear, most of it quite nice...I wish him luck.

Chris Ryan [21030691]

$3450 now. (!?!)

This was the winning bid. This equals the price paid for 21030668 in October 2005 [see Really Big Chroma Inflation].


Olli [21010284]

hi, i finally installed the CC+. very easy indeed, and it works immediately. need i add that this is a great job, guys?

Rob Belcher [16330123]

That reminds me, i have been talking to my tech in the UK, who is installing and repairing both my Chroma Expanders. On the unit that has the CC+ board installed, my tech has suggested to me that if i want to keep it working without problems i should think about replacing the PSU too?

What do you guys think about that? Has anyone else done it?

Luca Sasdelli [21010226]

I'm just doing it these days. I've left my Chroma unused for one year, and when the CC+ arrived, the PSU did lack +5V analog. So I've purchased a MeanWell and I'm going to finish the small PCB with +5V and reset circuitry.

I don't think there should be any relation between the CC+ and the PSU type. Maybe the suggestion your tech gave you is about the expected lifetime of your PSU, more or less what just happened to me :-)

David Clarke [21030085++]

CC+ & Power Supplies

It's a basic reply - but at a high level, if the Power Supply (original or otherwise) is working OK, then there may not be a need for a change at this time.

If the power supply is already exhibiting problems, then some update is warranted - either bringing the original back in spec., or by using a replacement.

[The choice of going with the original or using a replacement is really independent of the CPU board in use. If the power is good - either the original Chroma CPU or the CC+ will work fine.]

CC+ Remote Control

Werner Schöenenberger [21010114]

Dear Sandro and David, hi list

I really like the CC+, it is great fun and works perfect. In the meantime I also started to control the Chroma with some external boxes by using the MIDI CC commands. Since I do not own actual but some legacy controllers (Roland MCR-8 or P&G MM-16), the external control does not work optimal. So I thought, I could post some ideas or suggestions which might be implemented in a future version.

  1. More than one custom MCM, selectable by a CC command (low priority)

    The MCR-8 only has fixed CC commands that will be sent - so it only is possible to address 32 parameters with this device. If the CC+ board would offer about 6 customised MCMs that would solve half of the issue. Since the MCR-8 has "function keys" which send a MIDI CC command, selecting these MCMs by a CC command would allow to use more than one "page" of 32 parameters to control the Chroma. E.g. CC#125 would select MCM#1, CC#126 would select MCM#2, etc.

  2. Auto-Scale Parameter

    The MM-16 always sends CC data in the range of 0..127. So if a parameter in the Chroma only has 7 steps, only the first 5% of the fader can be used (it is repeated 20 times). So if the CC+ board would offer a mode that automatically scales down the values from 0..127 to 0..7 that would be helpful. Maybe the mode could be switched on/off with a CC+ Parameter (e.g. P26).

  3. Parameter-Send by CC

    A further mode would help users of controllers with automated faders (or belts). If there would be a mode which sends all parameters as MIDI CC commands when a patch is selected, the attached device would be able to adjust faders and pots to the current sound. This would make it easier to make small changes to the sounds and would give an overview of the parameter settings. Maybe this mode also could be switched on/off with a CC+ Parameter (e.g. P27)

Additionally I do not understand the need of the different MIDI CC mode (P24). In my opinion only the "Prog" mode is needed since all changes to Prog 0 are gone whenever a Program Change is made (as long as there was not a patch save done before). What is the advantage of the "Inst" mode?

Go to next message in thread (April 2007)