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ChromaTalk Archives: February 2002

Fwd: Chromas for sale

Chris Ryan [21030691]

Begin forwarded message:

From: Ken Bonebrake
Date: Wed Feb 06, 2002 06:05:59 PM
Subject: Chromas for sale

I have 2 Chromas and 2 Chroma Expanders for sale:

  1. Chroma: In great shape, fully functional. Has only been moved twice. With case, Syntech midi interface, dual pedal, volume pedal and Chroma cable. I have the manual, cassette and cassette interface cable. 1400 US
  2. Chroma: For repair or parts. All parts seem to be in place. When powered up only a couple of lights go on. The cabinet has a lot of foam stuck to it and needs cosmetic work. All sound cards work. With dual pedal and volume pedal. 600 US
  3. 2 Expanders: For repair or parts. All parts seem to be in place. Nothing happens when turned on. Between the two there are 8 working sound cards and 8 nonworking sound cards. 550 US with working sound cards, 400US with nonworking sound cards.

Buyer pays shipping.

In addition: One volume pedal (never used, in box), one extra sound card not working, and a Chroma Service Manual. (I also have an Apple 2e with the Chroma Music System cheap!).

Contact: [e-mail address removed]

Kenton / Syntech MIDI interface

Matt Thomas [21010021]

Hi All,

First I have to say that Chris's Chroma site is incredibly impressive, I've not come across anything half as comprehensive for any other instrument I own. The enormous amount of info and informed opinion on the site was an influencing factor on my decision 'to go Chroma'.

I've now acquired a Chroma of my own, complete with a non-working Kenton MIDI interface. I'm absolutely not a technician, so having looked at the internals and checked that there are no dangling cables or anything obvious I've reached the limit of my abilities. So I rang Kenton and asked for any tips, but all they are able to do is charge me for a repair. By the time I've shipped to London and back plus service costs I figure I may as well just buy a Syntech for $200 and forget the dead (and I gather inferior) Kenton.

So my question is does anyone here have any experience of this situation? Obviously my biggest concern is that the Kenton mod might affect the workings of the Syntech (which I gather simply plugs into the Chroma's interface). Bearing in mind I've never even seen the Syntech and know little about the Kenton even the most seemingly obvious info will help.

If it will help with a diagnosis I can tell you that when I go round the back of the Chroma and look at the rear panel there are three MIDI sockets to the left of the computer interface, seemingly in place of a vertical rectangular panel with top and bottom screw holes. What went here originally?

Erik Vellinga [21010286]

Hi Matt,

Congratulations with you Chroma !

I myself own a Kenton interface and build in into my Chroma after trying to build an interface myself back in 1991. At that time in seemed the only MIDI retrofit available.

The Kenton kit is working OK since then but not the way you want it to work. MIDI velocity puts out only 50% of the real Chroma velocity. So you miss 50% of your great wooden keyboards dynamics . The Kenton kit only lets you control the Chroma parameters filter cut-off and VCA gain (volume). Programming the Chroma by PC is NOT possible using the Kenton kit. Besides that, your modulation pedals will not be sent by MIDI, SysEx is NON-compatible with the Syntech so you can not simply load the sounds you find on the Chroma WWW page into the memory of the Chroma. The Kenton kit does not let you use the Chromas multi-channel mode etc etc. I will not say it sucks, but almost.... It just does not let you use the features that makes the Chroma so interesting and unique. (playing the keyboard connected to a piano-module is great....IF you can boost the key-velocity to 150% (I use Cubase to do that for me).

If you want to get serious with your Chroma get yourself a real MIDI kit : the Syntech. Sorry KENTON, I have discussed this issue with John Price at Kenton a long time ago but, me thinks, it is not worth the effort (and money) anymore for KENTON with so little Chromas left....

About your problem:

MIDI in and MIDI out both don't work?? You can check if any data comes out of the Kenton by monitoring MIDI commands with a pc program like Cubase or any MIDI monitor. Maybe it is working but you do not know it...?

There should be a little button connected to the interface. This button lets you switch between programming the interface or MIDI-interfacing. I forgot about the colours of the wiring, my Chroma has just been put together again and I do not want to open it again to peek inside... it has to be in the ON position (I think it connects the black wire to ground for as far as I can remember it ) So, when this (black?) wire is not connected to ground the interface will not work!

If this does not solve your problem I advise you to find yourself a friend or family member who knows a little about electronics to do the right diagnosis. Find out first if the interface gets its voltage right. If that's OK it gets tricky. Be absolutely sure all the Kenton's wires are connected to the Chroma PCB and MIDI connectors on the back of the Chroma.

Doing a RESET (set split 50) will make the Kenton stop working so don't do that ! There can be (sorry, I forgot..) a lithium cell on the Kenton's PCB you can replace by a fresh one.

Besides that, your Chroma may be in need of new AA-batteries for memory backup and a bit of calibration and tuning of the VCO's and DAC before you can start enjoying your instrument. You can find info on this in the service manual at Chris's WWW page.

There used to be a black 'blind' plate there before your MIDI sockets came.

It is not possible to use the Kenton and Syntech at the same time. You will have to turn the Kenton of to be able to use the Syntech or vice-verca. I suggest you get your Kenton out of your Chroma if you want to use the Syntech, there is no use of having both of them.

You can download the user manual of the Kenton kit at:

The manual, along with self-install documentation, is now available from this site--Kenton kindly provided the information when they discontinued production of the kit at the end of 2002.

Good luck,

Erik (the Netherlands)

Rich Hilleman [21030351+]

Where is the keyboard.

I have 2 california shops that know both kentons and chromas.

Matt Thomas [21010021]

Chester in the United Kingdom, not too close unfortunately.

I'm really much more interested in replacing the Kenton than repairing it as I gather it just isn't up to the job. Are there any obvious problems anyone can identify with taking this course?

Paul Hackett-Evans [21010094]

Matt, You're near me!

Hi Matt!

You're in Chester, I'm in Manchester. An hour's drive! It's nice to meet someone from my locality through the Chroma group. I used to work in Chester so I'm very familiar with the locale, small world!

Now, your Kenton interface.... I'd heartily agree with Erik - the Kenton interface [info, self-install documentation, user documentation (PDF)] is nothing like as good as the Syntech/Chroma cult. Don't bother trying to fix it unless it's really cheap to do or you have no alternative.

The gents at Kenton electronics are very nice and helpful guys, good to do business with, but their design just isn't as advanced as the Syntech one.

The Chroma Cult Midiconverter is really good. I had one of the original ones in the 80s, which was lost while my Chroma [21010094] was in hyperspace for the last 10 years. I remember using it with Notator on the Atari. The Chroma served as my MIDI master keyboard, and as a multitimbral sound source driven by Notator. I also used the Chroma Cult interface to save and load patch data via sysex.

I've spent the whole of this year restoring my Chroma with the help of Roy Paynter, who's a real gem of an engineer, and I've bought one of Ken Ypparrilla's new batch of Midiconverters to replace the one lost in a black hole. I've just (tonight!) bought a copy of Emagic's Sounddiver 3 on EBay. It's the best MIDI patch librarian you can get, and it can be used to store and edit all parameters of the Chroma with the Chroma Cult Midiconverter. Great! But not with the Kenton.

If you want to use PC/Mac-based patch librarians/editors or get the most out of the Chroma's features in sequencing or as a Midi controller, the Syntech/Chroma Cult one's definitely the way to go. Ken has been producing them again, he might still be able to supply you with one. They arrive quickly, very securely packed, and with full instructions.

I'm not a serious techie myself (Roy's the UK's true expert), but I know my way around the Chroma after all the restoration work. if I can help you at all, please mail me: [address removed; the Service page includes contact information for Roy Paynter.]

I don't have much free time at all, but I'll gladly help you out if I can.

I'm travelling to Roy's and back at the end of February. If you need his services (is your Chroma working well?) let me know.

By the way, what's its serial number? Where did you get it from?



Erik Vellinga [21010286]

RE: Chroma: Matt, You're near me!

Dear Paul and Matt,

I agree with you about Kenton. John Price was very helpfull in giving information about the Chroma kit. I do not intend to put Kenton in a negative light. I know their products are more than okay. It's just that in this perticular case the Cult interface is a better choice...



David Clarke [21030085++]

Kenton Sysex?

H.T.Vellinga said:

Besides that, your modulation pedals will not be sent by MIDI, SysEx is NON-compatible with the Syntech so you can not simply load the sounds you find on the Chroma WWW page into the memory of the Chroma.

Does the Kenton interface allow sysex memory dumps? If so, can someone with a Kenton interface load one of the factory sets (available from the Chroma site [Patch Downloads]) via the cassettee interface and then dump them to Kenton sysex format? If someone can do that and send me the resulting sysex file, then I'll write a mini convertor to convert from the Kenton format back and forth to other formats (and we can add it to Patch Conversion Tools).

Erik Vellinga [21010286]

RE: Kenton Sysex?

Hi dave,

I have several dumps from my kenton. It would be great to be able to load the patches on the site into my Chroma ! Getting a new sprit in the beast ! I will try a dump tomorrow.

My God, i must have spend days or weeks on this. I hope I can find the time to get you all the info I have on this one...



Chris Ryan [21030691]

Syntech/Chroma Cult MIDI Retrofit

On Friday, February 8, 2002, at 02:49 PM, Paul Hackett-Evans wrote:

If you want to use PC/Mac-based patch librarians/editors or get the most out of the Chroma's features in sequencing or as a Midi controller, the Syntech/Chroma Cult one's definitely the way to go. Ken has been producing them again, he might still be able to supply you with one. They arrive quickly, very securely packed, and with full instructions.

I received an e-mail from Ken Ypparila [21030229] just the other day. He told me that he only sold about half the new Syntech/Chroma Cult MIDI kits he built last year. As this seems to be the only decent retrofit for the Chroma, I'd encourage anyone who needs one to e-mail Ken (his contact information is on the MIDI Retrofits page at the site) and pick one up. Once this batch is sold, I doubt we'll be able to get any more (I'm tempted to buy one as a back-up). He may even be willing to reduce the price, I'm not sure.

Matt Thomas [21010021]

Re: Matt, You're near me!

Hi Paul,
Nice to hear from someone in the area, funnily enough I was in Manchester last night. Thanks for your generous offer regarding your trip to Roy Paynter, I think my Chroma is currently good as far as they go (which is to say that anywhere between zero and three voices might give errors on start up). However, I am not giving the Chroma the use it deserves due to the absence of MIDI; once I sort this out and start relying on it more I might run across other problems. Where in the UK is Roy based, and if you don't mind my asking, what sort of rates does he charge for his work?

In answer to your question, I got my Chroma from FunkyJunk, one of the big vintage gear specialists in London. They're normally only concerned with outboard, mics and mixing desks for large studios, but the Chroma was personally owned by the MD of the company. I picked it up for £800 in reasonable working order, no case but no wood-rot either so a fair compromise. I was particularly pleased to discover that the serial number 21010021 placed it as one of the 'first fifty'. Having since looked in the Chroma registry I've discovered that the previous owner from three years ago has already registered it. Interestingly it is described as having an internal KMX converter but when I looked inside I found the Kenton unit I previously mentioned.

I'm not sure what the deal is with updating another person's registry info. Any precedents? Also regarding the registry I know one other Chroma owner of many years standing in Liverpool, I'll see if I can get him to tell me the serial number and background story of his.

Chris Ryan [21030691]

Re: Matt, You're near me!

I'm not sure what the deal is with updating another person's registry info. Any precedents?

Yes, there are now several in the registry. I've just been adding the new owner's information following the original (or at least previous) one.

Paul Hackett-Evans [21010094]

Replying to Matt

Just so's you folks don't all think I'm ignoring Matt's last posting, I've replied to him personally rather than via the group. This is because I don't have Roy Paynter's permission to post his location on the internet for all the world to see. But I can put you in touch if you need Roy's services.

See you later alligater!

Chris Ryan [21030691]

Re: Replying to Matt

Actually Roy's e-mail address is listed on the Service page--along with a disclaimer about contacting him through Paul if it's urgent.

pinging Phil Dodds

Dave Bradley [16330135]

This is my biannual ping inquiring after the Phil Dodds interview...

Chris Ryan [21030691]

Quite coincidentally, I finished up with Phil just the other day. Believe it or not, after all this time I am finally going to post it this weekend! Stay tuned, it's more than just Phil Dodds ...

Pluggin' pc audio to Cassette I/O

Sandro Traversi [21010217]

Hi all ,

I'm trying to dump factory .snd banks thru the cassette interface , but with no result.

I'm using Cool Edit 96 on a P100 laptop and I can actually hear from the audio out all that mess ... I builded also a cable - mono 3,5mm plug from pc audio out to a DIN plug pin 3 to ground and pin 5 to "tape recorder" ) as reported in previous ChromaTalk messages Once plugged everything , I tried several times without results.

I also noted a Dave's message pointing that tha audio out has to be greater than 1,9 V. Than I measured by a DVM my audio out and it's really lower (0,03v).

So better keep away my pc and try with a real tape recorder ? Any hints ?


Josue Arias [21010162]

Try using the Headphones output instead the line output from your laptop, It will put out a greater signal level.

Paul Hackett-Evans [21010094]

Pluggin' PC audio...

Hi Sandro,

If you're using a phono (line-level) output from your soundcard, it might not have the signal strength you need.

Does your soundcard have a headphones output? Or the PC's front panel? That should provide enough signal for your Chroma to recognise the sound dumps. You can vary the signal level using the PC's volume contol to achieve a level which the Chroma is happy with. Always start with minimum volume then gradually and gently increase it until the Chroma recognises the dump. It's probably a good idea to check using your meter what the max level will be before you start to feed it into your Chroma, just for the Chroma's safety.

Be careful, though - NEVER use a loudspeaker output to try loading patches into the Chroma, it will overload or fry your Chroma's circuitry!

Personally, the best results I've always found have been from using a cheap (GBP 25.00) mono cassette recorder. Basic & simple, but it's the kind of machine that tape-dump circuitry was intended to be used with. So if a phones level output from your PC doesn't work, get a cheap mono tape machine and that should work. If your patch library is stores as wav files on your PC, you can record the PC soundcard output to the cassette then go from there into your Chroma. A long process, but it will work.

NB don't use a stereo tape machine as the two channels (left and right) can cause phase cancellation in the tape dump signal and the information will be distorted, so the dump won't be as reliable.

Good luck,


Philip Dodds/Tony Williams Interview

Chris Ryan [21030691]

At long last, the Philip Dodds interview is done! I know, I know, it's been almost two years. Mr. Dodds has been very busy, but I think the wait has been worth it. As an added bonus, Tony Williams (whose major contribution to the Chroma project was the groundbreaking Apple II sequencer software) also participated in the interview.

Thanks everyone for your patience, and for your help putting together the questions. Enjoy!

Dave Bradley [16330135]

Thanks for your perseverance, Chris! It is a very interesting read. It's unfortunate that there aren't any 88 key Chromas hiding in the closet anywhere...

For the registry

Doug Terrebonne [21030114]

Hi Chris I guess I never added my Chrom to the registry so here's my info:

21030401 - I purchased this Chroma from a guy in Berkeley, California who said he got it at an estate sale. It wasn't working when I got it and I'm afraid still isn't. After buying it I opened it up and discovered all the EPROMs where corroded and oozing some white goo. I have since replaced the EPROMs with new ones (thanks to Chris Now for programming them). It powers up but with random LEDs lit and doesn't make any sound and none of the controls seem to work. I plan to troubleshoot the power supply next as I know this is a common problem area. Any suggestions would be appreciated. With some luck and assistance from the mailing list I hope to get it working again.

Murray Macdonald [21030276+]

The random LEDs you describe means that at least some of your power supply is working, but that your CPU is not succesfully running the program the clear the LEDs, or the program is running but the CPU cannot access the panel board. I would suspect that you CPU isn't oscillating running and try and prove that it is or isn't. This could be the case for many reasons. There are a few simple things to test for.

1) Power supply voltage. Measure 5.0 v on any of the TTL chips. This tests not only the power supply but also the cable and connector. The CPU and most of the logic circuitry to operate on 5.0 volts, so check to see that it is there. Any 74xxx chip (14 or 16 pin) will make a great test point. Take a volt meter and measure the voltage at the chip. It should be pretty close to 5.0, (I have one Chroma that runs at 4.63v, but I feel that's too low. It should be 4.9 to 5.1) Also check the other PS voltages, but I think the CPU and logic needed to clear the LEDs only requires 5V.

  • pin 7(gnd) & 14(+5) on a 14 pin.
  • pin 8(gnd) & 16(+5) on a 16 pin.

You can also check for 5V on the CPU Vcc is 5V and Vss is Gnd.

 1 -|Vss          /Halt|- 40
 2 -|/NMI          Xtal|- 39
 3 -|/IRQ         Extal|- 38
 4 -|/FIRQ       /Reset|- 37
 5 -|BS            MRDY|- 36
 6 -|BA               Q|- 35
 7 -|Vcc              E|- 34
 8 -|A0           /BREQ|- 33
 9 -|A1             R/W|- 32
10 -|A2              D0|- 31
11 -|A3              D1|- 30
12 -|A4              D2|- 29
13 -|A5              D3|- 28
14 -|A6              D4|- 27
15 -|A7              D5|- 26
16 -|A8              D6|- 25
17 -|A9              D7|- 24
18 -|A10            A15|- 23
19 -|A11            A14|- 22
20 -|A12            A13|- 21

2) See if the CPU is oscillating. Using a $20 logic probe (a priceless tool) or an oscilloscope, look at the CPU and see if you can see the address and data lines jumping around. If a bunch of the Address and Data pins (Ax and Dx) are changing (between highs and lows), then the CPU is oscillating and its little brain is trying to run. You can't really measure for this without a scope or logic probe. Most meters respond too slowly to see quick little pulses. Some new meters have a build in logic probes and frequesncy counters that will show logic states and count pulse rates.

Just to be clear, I am talking about looking for life on the 6809 CPU on the left side of the circuit board mounted on the rightmost side of the chassis (the one with the banks of memory chips, not the other CPU for keyboard scanning on the low density circuit board).

3a) If the 6809 CPU is not oscillating, then look into the oscillator and the reset circuit. Oscillators rarely die, but I have had to rebuild a crystal oscillator or two before. Oscillators are usually just a crystal two caps and a resistor. The oscillator(2Mhz) connects to pins 38 & 39. If I suspect this to be the problem I will often will junk the whole oscillator and rebuild it for 5 bucks. Sometimes CPU's won't oscillate becaouse the CPU is actually dead. The good news is that the 6809 in the Chroma s socketed, so just swap it out and test it with another. Often reset circuits are hooked to the power supply so that the startup circuit can know when there is enough power to allow the CPU to start oscillating and running. Pin 37 must be High (over 4 volts) for the CPU to run. I'm not sure if the Chroma power supply controls this or if its just a delay like on many other CPUs. Find the reset pin (37) on the CPU and check to see that it is over 4 volts.

3b) If it is oscillating, (the ultimate test for if the CPU is trying to run is looking for pulses on Pin 34) then you need to figure out why the CPU can fetch and operate enough of the program to clear the random LEDs as it usually does when booting. If it is oscillating but can not run the boot program (clear the LEDs), then I would start suspecting the address and data buffer chips or the RAM. It could also be an address decoding problem, but more than likely its a buffer or ram chip.

FWIW, the problem you have described sounds like it has nothing to do with the audio boards, unless they have a nasty short and are pulling down the power supply. You could even remove the audio boards to reduce the variables until you get your LEDs to clear. Focus on getting your CPU to run and the LEDs to clear, then pursue audio.

Good Luck,

--Murray Macdonald.

Chroma FS on Ebay

David Clarke [21030085++]

Just in case you haven't stumbled across it yet, there's a Chroma FS on Ebay - currently at $102 (no idea what the reserve is set at).

I have sent a note to the poster asking him to add his Chroma (and Expander) to the registry - but no response yet.

The Ebay item can be seen at: [URL removed; item 1512391409]

Fwd: Chroma "Carcass" For Sale

Chris Ryan [21030691]

Begin forwarded message:

From: Kevin Lightner [e-mail address removed]
Date: Mon Feb 11, 2002 11:16:23 AM

If you or anyone else you know might like a Chroma carcass, please let me know with an offer. I don't have the unit myself, but a friend would like to move it. Shipping is up to the buyer. As far as I know, the case is included.

(large pics ~450K each)

Obsolete URLs removed.


-- Regards,
Kevin Lightner

Here are the pictures.


Fredrik Bechmann

Hi all you Chroma wizards!

My Chroma is dead! It never powered up this morning. Since I'm a bit of technical idiot when it comes to such things as turning the Chroma inside out, I thought maybe some of You might have a good idea of where to start!...

:-) Fredrik

David Clarke [21030085++]

Fredrik, can you describe what you saw/what you didn't see? When you turned it on, did any of the lights come on, or was it totally dark (as if there was no power)?

If some lights did come on, did they come on and stay on - or did they flash a few times?

If you tried to power it up a couple more times, did it behave the same way?

Paul Hackett-Evans [21010094]


There is an internal fuse on the Chrma's power supply board. It's inside the Chroma at the far left end looking from the front of the synth. Check that it hasn't blown, (Also the fuse in your mains supply lead). If it has blown, the question is: Why?

Be careful, there are a couple of diodes on the I/O board ( the long circuit board behind the membrane switch panel) which can deteriorate with age. On both of the Chromas I've known about recently, these diodes failed and caused the fuse to blow. They also did something to the power supplies which needed an engineer to repair (ie the PSUs went bang! But they were easily repairable). I'm not sure exactly which diodes they are. maybe someone else can advise. If not, I'll find out from my engineer friend in the next week for you. If they caused your problem you'll need to get them replaced.

If in doubt, I'd get a qualified engineer to look at your Chroma. Better safe than sorry. See the service agents list on Chris's site.

Good luck

Fredrik Beckmann

Hi David!

Thanks for Your response. Well... It is completely dead. Nothing happens at all when I turn it on. Everything is totally black. I must admit though, that it might have happened a couple of days ago since I power up my studio every day, but do not necessarily use the Chroma.

Expander on Ebay

Paul Hackett-Evans [21010094]

Hi folks!

Just to let you know there's a Chroma Expander for sale on Ebay which ends tomorrow.

It's in the States. I'd bid myself if I could afford to import it to the UK but the import taxes are crippling, so it's not for me.

I hope this helps someone who wants an expander.

Best wishes,