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ChromaTalk Archives: January 2007

About The Site

Chris Ryan [21030691]

A bit of a diversion this month: I've received a number of requests for information about the Chroma site, its history, design, and implementation. I have expanded the "About This Site" page into a section that includes information on the origins and growth of the site; data on visitors, referrers, and page popularity; an overview of visual and interactive design considerations; and a discussion of Web standards (XHTML/CSS) issues and the PHP framework I put together for the site. I have also broken out contributors onto a separate page.

The site enters its ninth year in February, and over the years there have been over a million page views, with about a third occurring in 2006. There were over 38,000 visitors last year, the best year ever and about five times the number of visitors in 2000. Thanks everyone for your continued participation and contributions.

Happy 2007 to all!

European CC+ update

Sandro Sfregola [21010294]

In a previous message to the list (European CC+ update [December 2006]) I stated "...the parcel I was waiting for unfortunately got lost (and several thousands euro with it), so I had to reorder the components...".

Luckily this is not true (it was a typing error): I haven't lost "several thousands euro" of electronic components but "several hundreds euro" that is a little different!


Happy 2007!

Jesper Ödemark [21010135]

...but millions of Lire! ;) (sorry, couldn't help myself)

Happy new 2007 all Chromaboys and Chromettes!

Luca Sasdelli [21010226]

Uhm ... yeah :-) Well ... I really hope that Sandro didn't lose that much money ...

Happy New 2007 to everybody too

Sandro Sfregola [21010294]

European CC+: 2nd batch update

A quick note just to inform all the 2nd batch European CC+ customers that I'm working on the latest details; the boards and relative accessories will be shipped within days. I will advise individual customers just before shipping.

Krisnallah Sumy [21010282+]

Re: European CC+: 2nd batch update

Hi this is nice news I was just calling sandro's name in talks with my woman Explaning the waiting on the european side of the globe since, she has to backup all decision by the force of showbiss

Question ???

Am I Krisnallah sumy in the upcoming second batch for cc....

Olli [21010284]

cool! thanks for the update sandro

Jesper Ödemark [21010135]

Splendid - I'm so looking forward to mine... I've checked with my house tech to sort out the programming of the Doepfer Pocket Dial to go with it.

I'll keep the list posted once there...

Re: SoundDiver for Chroma

Go to first message in thread (December 2006)

Malte Rogacki [21010091]

I have this (along with the Polaris plug-in), but I'm not sure what legal implications there may be in posting it. It was developed by Malte Rogacki [21010091]; Malte, what do you think? Is this something that you still own rights to? If so, can I make it available on the site?

You sure can make them available on the site; after all they are pretty useless without the actual SoundDiver program (of which they were part anyway).

On the other hand the original request was strange enough to raise the question if it was meant serious. The list included quite a number of synths that don't even have MIDI or SysEx capabilities...

New to list with some questions - Power Supply Voltages

Heath Finnie [21030175]

Hi everyone,

My name is Heath and I just picked up 21030175 from Ron Joseph [21030042+] (who I finally met and is a great guy) and it won't start up. After doing some preliminary checks, here is what I've found:

On the power supply I am getting +12 and -12 and in the the +5A locations I'm getting 5 Volts but in +5D location I'm only getting +2.23 Volts. Does the 5V adjustment effect both the +5A and D voltages, or just one? Any idea why I wouldn't be getting the full +5D?

(The exact pins that I'm getting +2.23 from are J2 - pins 2 &5 and J3 Pin 5)

Thanks for any insight and I'm glad to finally be a Chroma owner! I think Ron will point out the other odd differences between this Chroma and others he's seen.

Matrix [21030220]

Howdy Heath. Good to see you here. : ) Congrats on the Chroma, it's in a league of its own. I'll leave the help to the more experienced. : )


yah, with Matrix promoting Chroma all over his site now, it probably cost you triple as much : )

Heath Finnie [21030175]

Well in checking the voltages the humming power supply just went silent and all voltages fell to 0. So it looks like I will need to replace the whole PSU afterall.

Stu Ervin

probably just blew a fuse. these things can be fixed. despite all the bad talk about them, the power supply is actually pretty robust. the more troublesome question is whether something ELSE is wrong deeper in the machine, which causes the power supply to go down.

that can be hard to find...

Greg Montalbano, Analog Synthesizer Service

First thing to do is disconnect the power supply plugs from all the boards; check each power pin going into each board for short to ground. It frequently happens that one or more components (on one or more boards) has shorted or died, and is bringing the power rail down to ground. Most likely components are bypass capacitors (particularly tantalum); also possible are ICs (CMOS, opamps, etc).

A little systematic checking with a continuity meter can tell you a lot about what's going on.

Heath Finnie [21030175]

When I posted initaially with the voltages, it was with all the power supply plugs already disconnected. So it was with everything disconnected that I was getting the +2.23V on the +5 digital pins.


John Leimseider [21030434++]

It's probably the filter cap or the overvoltage protector... The fuse is blown now almost for sure. You can run it fine without the overvoltage protector... It's really there to protect the filter cap.

Ron Joseph [21030042+]

Happy new Years to all,

I just got back from Boston where I picked up Chroma 21030175. This was the free Chroma generously given away by Brion Robison, who by the way is a great guy. We spent a little time over coffee talking about synths in general as well as this Chroma. Brion said this Chroma was part of the M.I.T. media lab during a project w/ Atari. ( I vaguely remember someone else claiming a Chroma from an Atari lab, anyone remeber who?) The Chroma itself was in great shape cosmetically. Brion did a great job removiong the Chroma rot. Internally she seemed fine, but she didn't power up.

When I got her to Heath's house we reseated all the voice boards and reseated all the various connections. Still no go. I did notice that several voice cards had bent connectors at the bottom where the pins connect to the mother board. Could this be the problem? Also, we tried starting her up w/ various numbers of voice boards in case the connections to the mother board were causing a short. We even tried starting it up w/ no voice cards. Still no go. We tried a couple of other things but after a few more failures decided to try the list for help.

The Chroma should be listed under Heath's name in the registry as he will be her final owner once we figure out how to get her up and running. The Chroma came w/ 2 pedal boards, an expression pedal and a cable to transfer patches. No manuals however there was a large copy of the parameter chart.

As a final note, the action felt slightly better on this Chroma in comparison w/ my other 2. I don't know if this was just an individual difference or something to do w/ the different keybed. It felt slightly heavier, less clacky and the release felt more fluid. Congrats Heath on your new Chroma and thanks in advance to everyone on the list for your help.

Don Tillman

Atari Chromas

Brion said this Chroma was part of the M.I.T. media lab during a project w/ Atari.

My memory tells me that there were two Chromas and one Chroma Expander at the Atari R&D Lab, and one or two flight cases, and some custom built computer interface equipment.

The Atari R&D Lab closed down in '85 or '86, and Symbolics purchased most of the equipment. The goal was to get a good price on Atari's DEC VAX 11/780 computer, and get all the other stuff thrown in for the deal.

What's Symbolics? Symbolics was a company that was founded in '79 by a dozen folks from MIT's Artificial Intelligence Lab to commercialize Lisp Machines, computers that natively run the language Lisp. These were awesomely cool computers which implemented graphics displays, windows and the mouse years before the Macintosh existed. I worked at Symbolics from '83 to '88. The company was very successful for a while, it went public, and was the very first "dot-com" (I mean that literally, it was the first to sign up for a .com domain name). Sadly Symbolics wasn't able to compete in a marketplace directed toward commodity computer platforms, and the company is no longer around. I don't know what happened to the Chromas; I think they were sold to a couple employees for cheap as the company was closing down some operations.

So anyway, yeah, I got to play the Atari Chromas alot. They were very nice machines and they convinced me to get my own Chroma a few years later.

Heath Finnie [21030175]


Well pulling out the fuse (that looks good to the eye) I'm getting no continuity from it. So it seems that I will need to replace the fuse first and then continue onto the +2.23 digital volt issue.


David Clarke [21030085++]

Heath, supporting the ideas in the earlier notes from the other folks, the good news is that the 5V digital issue shouldn't be a big one to solve. (Most of the parts used in the power supply circuit are still available.)

From the earlier note, one of the first/easiest things to do is look at the voltage on the top of the big filter cap (C3). If the voltage there is 'good', then the problems lie between it and the P2 connector.

If the voltage there is already bad, then remove the board off the top of the filter cap [remove screws, remove board - reinstall screws and wires to top of cap]. That will let you know if Z4 has gone bad.

If you don't get lucky with that, you can start to work backwards from the P2 connections (or C3, if the voltage is already 'bad' there) to see where the 'good' voltages disappear (i.e., are you OK at C3, and then bad after that - are you good at the rectified stage from the cathodes of CR1, CR2, etc.)

(The schematics are available on-line from the Chroma site - and so if you have a 'scope or multi-meter you should be able to pretty quickly narrow down the general area of worry.

Good luck - and be sure to let us know how you make out.

Heath Finnie [21030175]

Just for an update, I checked the voltage across the big filter cap (C3) both with and without Z4 and get 2.23 or thereabouts. So it looks as if the issue is before that!

John Leimseider [21030434++]

If the filter cap is open, the meter will read low, because it's looking at the average DC. Check with a scope, or measure it on AC. If you have a couple of volts of AC, then the filter cap is open. It's pretty common for them to fail. Replace it with a Mallory CGS503U016V3C. It's a 16 volt version, much better. Throw away the overvoltage protector...

Heath Finnie [21030175]

Well I checked the capacitor all by itself and it's bad. So I'm ordering a new 16V 50000uf one from Mouser. Hopefully that will get it up and running at least. Then eventually I can replace the PSU alltogether and do the CC+ upgrade.

Olli [21010284]

i can see that AMSTEL exists in the US... whaow... well THIS analogue, hehe

Heath Finnie [21030175]

Is there any source to get a new PSU for the Chroma, but one that has all the modifications and connectors all set so you could basically drop it in? Sort of like the CC+ boards? I want to upgrade the PSU, but am nervous about doing mods to the new PSU. (Basically I would hate to screw things up with it). I'm also asking for people who have no real soldering/tech knowledge. I have some, but am just curious.

David Clarke [21030085++]

Is there any source to get a new PSU for the Chroma, but one that has all the modifications and connectors all set so you could basically drop it in? ...

Heath - I'm not aware of any 'complete, out of the box' offerings - although I do have a recollection about someone making up a little circuit board for the add-on circuitry (if my memory is any good, the details should be in the list archives on the Chroma site).

The 'should I keep the original or put in a new PSU' topic is very much a Coke vs. Pepsi sort of discussion. You'll find a lot of opinions on each side.

From my own perspective, after the initial repair work to get them going, I've been happy enough with the original power supplies that I haven't considered removing them from the Chromas here.

If you can revive the synth with a single $20 part (the cap) (and perhaps a few other small caps - e.g., the capacitors in the reset circuit) - then you're probably ahead of the game.

My $0.02.

Heath Finnie [21030175]

Thanks for the info. I'm also guessing that the CC+ helps a lot too since it uses a lot less draw on the PSU.

Heath Finnie [21030175]

Hi Everyone,

Well I got the capacitor from mouser and it's installed. Now it powers on, all the LED's blink and then I get "err 4" I've moved this voice card all over the place and I get "err XX" where ever I put it.

Should the unit make sound with just the remaining 7 voices? I can select patches and the err message dissappears....

And even stranger, I moved the board back to spot '0' and now I get "err 0" when I turn it on, but if I hit auto tune a minute later, I get "err 5" instead.

I've re-seated these a bunch of times and in different locations

David Clarke [21030085++]

Well I got the capacitor from mouser and it's installed. Now it powers on, ...


all the LED's blink and then I get "err 4" I've moved this voice card all over the place and I get "err XX" where ever I put it. Should the unit make sound with just the remaining 7 voices? I can select patches and the err message dissappears....

Yes. The failed board(s) will just be excluded from the voice assignment, and any/all remaining boards should be able to still play just fine.

Given the power supply issues, I wouldn't be surprised if the RAM has got confused and has lost all patch memory. To see if you can get some sound out of the Chroma, create a 'scratch patch'.

Press both the Edit A and Edit B buttons.

Press and hold down the 'Param Select.' While continuing to hold down that button, press each one of the 50 numbered buttons on the right hand panel. This should create a scratch patch (basic settings) that can be heard.

If you don't get any output, check out the Out 0, Mono Out and the XLR main out (if you can). If still no sound, start tracking backwards, checking to make sure there's audio making it to the EQ board.

Good luck.

Press and hold down both the edit A and edit (hold down the EDIT A and EDIT B

Heath Finnie [21030175]

No sound


sorry about all the e-mails but I read in the manual that if a voice errors out that it just disables it and the others should work(?) Well I'm not getting any sound out of the machine.

Heath Finnie [21030175]


Here's what I did. I selected both Edit A and B at the same time and then ran through all 50 parameters (while at the same time keeping "param select" held down and still nothing. No sound out of Out 0, XLR or mono.

Heath Finnie [21030175]


I tried what you suggested and I noticed that hitting multiple keys are not causing the LED to flicker in the least. Maybe that's the issue? How would I know if the right/correct RAM is installed?

on the Computer board Z29 - Z36 have stickers on them that say the following:

  • Z29 - R12C0
  • Z30 - R12C8
  • Z31 - R12D0
  • Z32 - R12D8
  • Z33 - R12E0
  • Z34 - R12E8
  • Z35 - R12F0
  • Z36 - R12F8

I also mentioned that I noticed a couple of cut wires at the output jack. At first I was suspicious that these might be causing my lack of sound, but checking with the schematics, all the correct wires are connected to the high Mono out and Balanced out which is what I'm using.


David Clarke [21030085++]

How would I know if the right/correct RAM is installed?

on the Computer board Z29 - Z36 have stickers on them that say the following:

  • Z29 - R12C0
  • Z30 - R12C8 [...]

The stickers indicate that it is Rev 12 code which is installed, but it's not possible to tell just by those tags if its code for a Chroma or an Expander.

An easy way to rule that our is to press each of the 4 buttons in the "Two Program Linkage" section on the panel. If all 4 buttons respond, then you've got Chroma (not expander) firmware.

You'll also want to ensure that there is a chip installed in the Z33 location on the I/O board (the keyboard scanning firmware) and that there's a connector plugged into J20 (the keyboard data).

Beyond that we're back to checking some of those other things (such of presence of audio at the EQ board, correct orientation of connectors on that board, etc.)

(The Interconnection Diagram 2 schematic will let you double-check the wiring connections on the back panel).

Heath Finnie [21030175]

Sorry for all the e-mails but I have a new development. I get an output out of Quad 2 (but only quad 2). All the patch memory seems to have been wiped clean. I need to clean (I'm guessing) various key contacts as some keys hold the note where as some don't sound at all.

What is the best way to clean the contact (and to check the contact to make sure if the problem with the key is actually the contact or something different?


Heath Finnie [21030175]

Thanks everyone!

Thanks to everyone who helped me get the Chroma back up and running. I re-soldered a bunch of wires to the output jacks, replaced the big cap on the PSU and now everything works as it should. The only issue with the Chroma seems to be an error on board 0 and occasionally 5. All keys are working as they should now that I bent a few contacts back into shape.

Now if only there was an easy way to load the patches back into it (no cassette cable)

Jesper Ödemark [21010135]

Re: Thanks everyone!

Build a cassette cable or load from a computer via midi interface (if you've got one). I've transferred all the factory programs to CD and loads from there when needed...

Heath Finnie [21030175]

Re: Thanks everyone!

Actually, has anyone ever just changed it from the 5 pin jack to a 1/4" jack? Seems that would be a pretty useful mod...


Re: Thanks everyone!

Just use Midi Heath. It is easy as pie There are a ton of patches in mid and sys ex on the chroma page and free sysex utilities for mac and pc as well.

Jesper Ödemark [21010135]

Re: Thanks everyone!


No, since it an in _and_ out solution on one plug you have to either remove one function or add another jack which is a bad idea if you ask me.

I simply slaughtered the cable from an old monitor cable and added a small box (old film container in fact) with two female 1/4" sockets (one on each end) marked "load" and "save". The way I made it it also stops you from having both in and out plugged at the same time...

My two ören on that subject... ;)

David Clarke [21030085++]

Re: Thanks everyone!

...and now everything works as it should.

Heath - thanks for the follow-up. It's good to hear of another Chroma up and running again.

The only issue with the Chroma seems to be an error on board 0 and occasionally 5...

Before getting too worried about those boards, I would be sure to go through Section 5 of the Service Manual (Calibration and Checkout) - especially the setup of the DAC null and the trim procedure for the pulse width on the voice cards.

NOTE to all the folks with noisy/slappy keyboard action - the keyboard action/damper bar section of this same chapter should be checked out.

Now if only there was an easy way to load the patches back into it (no cassette cable)

If you want to create your own cassette cable, there's wiring information available in the mailing list/ChromaTalk archives.

For the sake of a quick load - you can just temporarily clip on to the connections directly inside the Chroma (since you have the top off anyway). If you're loading from a computer (e.g., .WAV file, instead of an honest-to-goodness cassette), then you don't care about the MOTOR signals or the 'record' output. Simply hook up the 'playback' input and the ground to the hot/ground side of the audio from the external source (PC, cassette, etc.) and you should be good to go.

Heath Finnie [21030175]

Re: Thanks everyone!

I would just use midi if I had it. I won't have it until I get the CC+ board (hopefully by the spring or summer. I'm on the waiting list ;)

FS : EES midi interface

Olli [21010284]

hi list,

if there are still some people without an interface for their chromas left here, i have one for sale. it's the EES midi interface, the functionality of which is said to be very large. i have used it only a couple of times after i got it with my chroma namely to produce some of the demo files on the bluesynth website.

it works and can read the soundbanks of the cooper interface on the website once the latter have been converted with david clarkes little conversion tool.

i can provide photos if anybody is interested.

Heath Finnie [21030175]

How does it work? Does it need the CC+ (which I plan on getting). Is it a box that connects to the back or do the midi ports actually go on the back panel?

Sorry for all the questions, I'm just new to Chromas ;)

Olli [21010284]

hi heath

if you get the CC+, i guess you don't need it as the CC+ has midi functionality. that is why i sell the interface. it connects to the chroma interface port in the back of the synth.

Jesper Ödemark [21010135]

Yes, I can recommend the EES - works splendid on my Chroma... though I'm looking forward to my ordered CC+. ;)

Chris Ryan [21030691]

There are photos and other information on the EES interface at the site. See MIDI Retrofits: EES and EES MIDI Kit Documentation.

Reminder to check your Chroma's battery health

David Clarke [21030085++]

If you haven't done so in a while, it might be a good time to check the condition of the batteries in your Chroma.

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

If the displayed value is notably under 3V, probably time to change the batteries (the service manual says anything under 2.5V is bad).


(PS, if you wanted to check your Polaris at the same time - the buttons to push are: LF-D-1. Two or more LEDs in the assignable Control section indicates things are OK.)

Jesper Ödemark [21010135]

You're great David, the lists own little doctor! :) I promise to check my patient before the end of the day, good to know if I need to exchange it while in there installing the CC+ (when that arrives).

Chris Ryan [21030691]

The great news is that the CC+ renders the batteries obsolete.

Jesper Ödemark [21010135]

Might be an idea to remove it from it's place then I guess... Bad idea to wreck anything with a leaking battery...

Dave Bradley [16330135]

Isn't the battery on the board that gets replaced by the CC Plus anyway?

Jesper Ödemark [21010135]

Yes I guess, but I'm not going to throw my original board away and when stored I'll remove the battery! Mine is exchanged/serviced already BTW...

Patches in wav format?

Heath Finnie [21030175]

On the patch download page I can only find one set that has been done in wav format. Does anyone know of anywhere on the web (or have personally) patchs in .wav format to load in?

Chris Ryan [21030691]

You can use David Clarke's patch conversion tools to convert from sysex to .snd format.

Heath Finnie [21030175]

Thanks Chris. Looks like I will be trying to learn terminal for OSX ;)

Chris Ryan [21030691]

It's not that difficult. Just be careful; you can get into trouble if you don't stick to what you know or are learning. Learning Unix for Mac OS X is a good short introduction. It's nice to have a bit of comfort with the terminal; it can really come in handy.

My first Chroma-related project for Mac OS X is a GUI version of the patch tools; I'm currently working on moving David's code to Cocoa (Objective-C). I hope to have something released in the next couple of months.


Olli [21010284]

hi sandro,

i might have missed the last update on the european batch, but was wondering if you have an idea of when approximately the boards will be ready. i am in no hurry but am just curious.


Michael Salmon [21030155]

i second that, i am kind of anxious since i want to start gigging with my band + chroma and midi would be a huge help

David Clarke [21030085++]

i might have missed the last update on the european batch, but was wondering if you have an idea of when approximately the boards will be ready. i am in no hurry but am just curious.

Olli - of course asking for an update is always OK; however, if you think you might have missed a post you can always check the ChromaTalk archives.

If you're not sure where to check, you can also use the 'search' from the main page.

An update was sent out to the list in late December. See European 2nd batch of CC+.

At that time, the best view for European customers was that the boards would hopefully be completed near the end of January.

{I'm certain that Sandro would let individual customers know if there's a substantial change to that date}.

i second that, i am kind of anxious since i want to start gigging with my band + chroma and midi would be a huge help

Michael - I believe you might be asking about the 'next' build of CC+ units (vs. the European build which is ongoing).

We will soon be letting the list know when we'd like to plan the next build.

Olli [21010284]

thanks david. sorry for the inconvenience.

It's Alive!

Randel Osborne [21030467]

I'm pleased to report that after 18 months on the bench, my Chroma has (nearly) come back to life!

I've replaced the power supply, the I/O board, and most recently installed the CC+ CPU replacement, which is a fantastic piece on engineering!

I am still ironing out a few bugs, and after repeated readings of both the service manual and Mr. Straw's fine repair guide, I have a few questions for the group.

The Chroma plays via MIDI, yet not via the local keyboard. Do you have suggestions for isolating the problem to the I/O board v.s. the Stack Switch board? Or is it simpler to just replace the Bank select decoders on the Stack Switch Assemblies as well as Z35 and Z35 on the I/O Board?

On one of my voice cards, I have a voice in which it appears that the filter remains open all of the time. Before I chase this down with the o-scope, are there any common failures which cause this symptom? Z19, Z20 and Z25?


David Clarke [21030085++]

On one of my voice cards, I have a voice in which it appears that the filter remains open all of the time. Before I chase this down with the o-scope, are there any common failures which cause this symptom? Z19, Z20 and Z25?

Randel - I've often seen the Sample and Hold amps go bad, as well as the S&H caps. You're probably now at the point of getting out the 'scope. A good place to start will be the output of the S&H amps for the filter (Z22/Z24). This will at least give you an idea as to which direction to start looking (i.e., backwards towards the S&H circuitry - or forward towards the filter itself.)

Question for Sandro: What will C2 be?


[No message body. See The Chroma CPU Plus (CC+): Postscript for information on C2.]

Chroma CPU+ : 3rd Build

David Clarke [21030085++]

We have once again placed enough people on the CC+ 'wait list' to justify another build of boards.

We propose to accept orders for this third build up until Friday, February 2nd (midnight, eastern time).

To ensure a timely order of parts for those who have requested CC+ boards, we would like to receive payment by Saturday, Feb 17th (approx. 2 weeks after the closing).

Within the next week we will be individually getting back in touch with the people on the wait list to see if you're still interested, to outline current pricing and to confirm your order. [David will be contacting the people from North America and Sandro will be contacting the people from the EU.]

If you're not currently on the wait list - but would like to have a board from the 3rd build - please be sure to get in touch before February 2nd.

If you believe you're on the wait list but have not received an e-mail from either Sandro or David within a week of this note - be sure to let us know.

Once again, thank you for your continued interest and participation.

Ron Joseph [21030042+]


Put me on the list for one board please. A question, Is there any difference in the CC+ board itself in terms of Midi connector/no midi connector. I purchased one of the first batch CC+ boards w/ the native midi option but never hooked up the cable as the Interface already in the machine worked fine.Still have a cable sitting here I'd like to use ;)


David Clarke [21030085++]

Ron - you should be all set. The CC+ units themselves are identical whether they're purchased with or without the cables (i.e., you should 100% be able to simply plug the original cable into the newer board).

program table layout problem

Martin Pavlas [21030450]


as I am working on the chroma knob-programmer (see posts from nov/dec [DIY solution for a potentiometer interface for the chroma (or other synths)/Some other non diy solution for a fader box] I have run into strange problems. Maybe somebody can help me out.

when I instruct my chroma to transfer packed definition of a program (initiated with 'Read Program' 0x02 command) everything goes just fine till byte 26. It should consist, according to the manual that I have, of four bits of 'cutoff mod 1 select' and four bits of 'cutoff mod 2 select' parameters for channel A. Unfortunately, the byte I get does not match settings of these parameters in chroma. all other bytes (greater than 26) seem to be bad too.

Has anybody had similar problem? Is the chroma interface manual (which is posted on this website) correct? I checked the archives and Dave's corrections, but did not find anything there.

For the rest the project is going along pretty ok. I will dump some more info here when I have more time.

Martin Pavlas [21030450]

right, I double-checked everything before sending the question to list - just not to make a fool of myself. Well, 5 minutes after posting it I found a bug in my source code. so it goes :)


Chroma in Sweden

Jesper Ödemark [21010135]

[Item 200069116781]

I know the seller so I can guarantee he's a good guy...

Chris Ryan [21030691]

This is Chroma 21040011, one of four Australian instruments in the registry (and the only one of those so far to have ended up in Europe). It has been sold.

Membrane switch repair

Ron Joseph [21030042+]

So, I recently recieved 4 voice cards that I sent out for repair (Once again JL [21030434++] at Cantos did a great job! Thnx!). I put them back into the machine and try to start a scratch pad. The only switch that doesn't seem to work is the Parameter select switch....ARRRRgh! The L.E.D.s all light up even on the Parameter button, the thumper thumps on all switches except the Parameter select.

Question to the group is "Am I missing something basic?" or is the switch dead. Also, How difficult is it to repair the switch? Sending out the panel would be a pain in the ...

Thanks in advance for the help....Ron

John Leimseider [21030434++]

MusicTek has replacement membrane switches for the Chroma and Expander... 818 506-4055...


Good luck getting parts out of them. I tried for months to get something for a Xpander they had, and got the runaround every time. Very dysfunctional. No offense meant JL, but it is not the same after you left MT.

John Leimseider [21030434++]

So I've heard... I still don't know where else to get the membrane switches...

Pedal on eBay

Chris Ryan [21030691]

Item #300073664060, no bids yet, ends January 29. From the description: "This Arp/Chroma Pedal is in good working order and just has some spotting on the case. The flash actually magnifies this. It can be used with any Arp product that has a pedal jack. It was also sold with Rhodes Chromas."

Is this true? Was the Chroma pedal the same as that supplied with earlier ARP products?

Here is the picture from the auction.

David Gowin [21030611]

I believe it was the same pedal/footswitch for Arp, Chroma and Chroma Polaris


pedal insanity

someone here is hilarious! : ) lol [Link to eBay auction for item #300073664060 removed.]

Lars Johansson [21030632]

Re: pedal insanity

I'm not sure I understand ?

I see nothing hilarious...


Re: pedal insanity

It may not interpret to scandinavian well : ) It was at $2 yesterday. Now thats funny! : ) LOL

The bids had increased to about US$60; the pedal sold later in the day for US$86.

Bob Brenenstuhl [21030894]

Re: pedal insanity

I thought the same thing, but then wondered if I just didn't get it....hmm...

Dave Blees [21030552]

Re: pedal insanity

Maybe I missed the hilarity you're referring to... unless you mean the price!?! sheesh.

I always thought the Chroma control pedal was the same as a good ol' DeArmond volume pedal, as seen in eBay auction 220076634547:

Although I suppose potentiometer values may vary...

Also, I noticed that the pedal pictured in the Chroma [Performance Manual]:

...looks suspiciously like an even more ancient DeArmond model.

* Does anyone know whether the Chroma is very particular about the value of its pedals' potentiometers? I've always wondered about that, since the Chroma's specs & manuals seem to rather ignore its "outboard" bits... (The pots in my pedals appear to be about 80K ohms.)


Re: pedal insanity

Ever watch Lost in Translation ? : )

Laugh a little , you will live longer

Chris Ryan [21030691]

Re: pedal insanity

"Mono phone jack - Ground on sleeve/Signal on tip. 120K ohms pull up to +12V. 0V to 5V effective input voltage." See Product Brochure: Variable Pedals and Specifications: Variable Pedals in the Performance Manual.

David Clarke [21030085++]

Further to Chris' recent note, the circuitry inside the Chroma has the pull-up to 12V (via the 120K resistor). The resistor in the pedal is connected in series with that.

To get into the 5V range, the resistor in the pedal would nominally be 86 ohms.

I think the actual Chroma pedal I have here is 100K; however, I would expect an 80K pedal to work quite well.

The pedal itself certainly does resemble the DeArmond ones - so much so I think they must share some common lineage.

Errored voices

Heath Finnie [21030175]

Hi everyone,

Any ideas why upon startup I'm getting "err 0147" and then upon auo tune seconds later I'm getting "err 01347"?

So then I turn it off and then on and then upon startup am getting "err 01347" straight away?

A third time turning it off/on gets me "err 0147"?

Thanks, Heath

(ps Also the voltage I'm getting from TP1 on the boards is about 2.8-3.1. Is that normal? I thought it should be close to 5v?

Jesper Ödemark [21010135]

It means voice card 3 is exactly at the limit of being in tune. I have had the experience with voice card 1 in my Chroma. It was during the hot summer and it didn't tune a few times. Now it's been OK for 6 months...

When your "3" is cold it's OK and when it gets hot it's not. That's how I interpret your description.

Card 0, 1, 3, 4 and 7 needs to be calibrated.

Heath Finnie [21030175]

IS there an easy way to calibrate the cards? The service manual's deception seems a little foreign to me.

All I do know is that TP1 (on all the boards) is giving me about 2.8 volts and the service manual implies I should be getting 5.V

Jesper Ödemark [21010135]

And the PSU is OK?

Heath Finnie [21030175]


I checked the PSU and all is well. I turned it on after a few hours being off and only getting "err 04" upon start up.

If I check the TP1 on the voice boards I get the following:

0 nothing
1 4.54v
2 2.1v
3 2.21v
4 nothing
5 2.32v
6 2.32v
7 2.10v

This was upon startup. After Auto tune I now get "err 01347" again. But yes, the power supply is fine.


David Clarke [21030085++]

Heath - is the TP1 location being measured with a volt-meter or an oscilloscope?

During the "Trim Procedure" outlined in the Service Manual, the signal at TP1 should be a 50% duty-cycle square wave, where only the top-most portion of the signal should be 5V. This means that the voltage you'll see with a meter should be in the neighbourhood of 50% of 5V, or about 2.5v.

The more asymmetrical the wave actually is, the closer to 5V or 0v you'll be.

You will want to use the scratch patch modified as noted in the Trim Procedure. With a 'scope you can then use the trim pots on the voice cards themselves to ensure the 50% duty cycle.

Jesper Ödemark [21010135]

Can there be a short circuit "stealing" voltage then? The voice cards 0 and 4 look suspicious indeed.

Heath Finnie [21030175]

Well my guess as to why 0 and 4 have no voltage is because the Chroma disables them since they error out. But I could be wrong....

Enrico Dibennardo [21030494]

I think you're right, in fact I avoided the check routine in a period in which one card was declared faulty by the routine while insead it did work perfectly. So I avoided the routine in order not to disable that "good" card. Did anyone experience something similar? Did I miss something in what I did?

MIDI control: CC+ vs. KMX

Andrew Dalebrook [21010180]

Hi all. I have the KMX interface already, but I would like to know if the CC+ MIDI data can be sent/recieved by the KMX, or would the MIDI connection kit be required to utilise all of the CC+'s MIDI functions?

David Clarke [21030085++]

Andrew - a connection to the CC+'s native MIDI interface is required to gain access to the new MIDI functionality offered by the CC+ (e.g., remote tune request, the ability to map in all chroma parameters via continuous controller or sysex, etc.).

The MIDI capabilities of the KMX interface come from the firmware which is running inside of the KMX interface itself. As such, the behaviour of the KMX interface won't change with the addition of the Chroma CPU plus (CC+) since the KMX did not change.

You would be able to use the KMX interface with the CC+; however, the MIDI functionality would be limited to what the KMX does today.

You can access the CC+'s native MIDI interface via the MIDI connection kit (which comes pre-assembled and pre-tested) or, if you prefer, you can build your own CC+ MIDI cable based on the wiring information provided in the documentation.

voice card sounds wrong but it in tune

Krisnallah Sumy [21010282+]

Hi need help Voice card no 4 of my chroma is in tune as in keytune at tp0---tp1 but the sound is wrong so tuning dus not help getting the right sound Can someone tell witch IC is malfuctioning it suspect on that has to do with oscilator or ......