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ChromaTalk Archives: July 2002

ARP Chroma Announcement

Chris Ryan [21030691]

Following up on the ARP Chroma discussion from May, I managed to track down ARP's announcement of the Chroma in the June 1980 edition of their "ARPeggio" magazine.

Mark Vail kindly sent a scan. He's not sure where the photo in the second edition of his "Vintage Synthesizers" book came from (the one that Erik posted to the list, which differs slightly from the one in this ad). Keyboard Magazine's executive editor had a look through their files and reports that there isn't much there on the Chroma.

What I find interesting about the text is that there's no specific mention of an external computer. The ad talks about the "dream" of controlling a computer (seemingly just the internal microprocessor) from the keyboard, rather than the other way around. Philip Dodds, in the "Rise and Fall of ARP" interview, talks about freezing the project at ARP "to configure the instrument so you could have individual channels under computer control." I wonder if, initially, there was little or no external computer control planned at all. (It's important to remember that personal computers were, at that time, still pretty much a hobbyist's item: the Apple II was around, but the IBM PC wouldn't be introduced for another year.)

Of course we all know what happened: the Chroma couldn't be finished before ARP went under. Interestingly, by June 1980, which is the cover date on the issue of "ARPeggio" with this ad, a trustee had already been appointed by a judge to oversee the liquidation of the company. So this was probably one of the last desperate measures to generate interest in the future of the company. If they'd managed to ship the Chroma, I wonder if they'd have been able to stay afloat for a few more years. Who knows; maybe they'd still be around and we'd be playing 2002 model Chromas.

Chris Ryan [21030691]

I asked Mark Vail whether "ARPeggio" (from which the ARP Chroma announcement was taken) was consumer- or dealer-oriented. He replied:

On one hand, I'd say it's consumer-oriented. Leading up to the Chroma page, the headlines are 'NEW PRODUCT DEVELOPMENT MARKS ARP IN THE 'EIGHTIES,' 'ARP 16-VOICE ELECTRONIC PIANO: SETTING NEW STANDARDS FOR PROFESSIONALS,' 'NEW 4-VOICE ELECTRONIC PIANO: IN TUNE WITH THE TIMES,' 'MIXING WITH THE RIGHT PEOPLE' (a multi-channel mixer -- the exact number of inputs isn't specified, but judging from the picture it's either 8 or 12), 'NEW AUXILIARY SPEAKERS COMPLEMENT ARP PIANOS,' 'FULLY EQUIPPED & READY TO ROLL' (about the new ARP Solus, built into a travel case), 'FREE! FLASHY SATIN ARP TOUR JACKET,' and 'GET YOUR SHOW ON THE ROAD WITH ARP.' But the on the back page, it's 'ARP POWERS UP FOR NAMM '80.' That tells me this publication was produced for dealers and publications.

After looking it over more closely, I'd say the second conclusion is correct.

Fred Warren


Just to add something to the discussion, I bought a replacement keypad panel for my Chroma (mine has a dent in it) and the replacement was from an ARP Chroma, complete with the ARP logo. Thus they did exist.

David Gowin [21030611]

Ahhh, where did you get the replacement panel?

Chris Ryan [21030691]

Just to add something to the discussion, I bought a replacement keypad panel for my Chroma (mine has a dent in it) and the replacement was from an ARP Chroma, complete with the ARP logo. Thus they did exist.

Although some have ARP-labeled parts, they were all "Rhodes" Chromas; certainly none were ever sold by ARP. The only ARP Chromas were probably shells for promotional photos (Philip Dodds says only one was produced before ARP went bankrupt), or early test units; see the "Different Back Panel" thread in May's mailing list digest.

Repair update

Rob Vandivier [21030396]

My Chroma is running again! Bob Benchic of Williston FL has managed to get it back to life. Here is the rundown so far: Repaired 6 voice cards (2 of them had problems that didn't show up on the self test). Repaired the keyboard scanning computer. Repaired the main computer reset circuit. Repaired an intermittant problem on main computer board (was causing an erratic display). Replaced several suspect components for prevenative maintenance purposes. Calibrated all voice cards. Cleaned keyboard contacts and sliders. cleaned the melted sticky foam from the outside.

It still needs refinishing and the mono outs are not working yet. The individual outs are. One time it auto-tuned with an 'err0123456' in the display, but it hasnt happened again. Set split 7 always comes up err 'x', I dont remember what number 'x' is. All programming parameters seem to be functioning normally.

Thats it for now,
Rob Vandivier
Orlando FL

Balanced Output Transformer - Hookup Aid

David Clarke [21030085++]

The circuit board containing the two transformers used to provide the balanced audio output on the Chroma has a 3-pin header row and a 4-pin header row. Unfortunately, the marker to indicate which end of the header is "pin 1" is on the underside of the board (not visible when it is installed).

This can lead to some confusion as to how to properly reconnect the wires if you've removed them intentionally - or if they've been pulled off unintentionally (by raising the panel lid too high).

The following diagram attempts to summarize how the wires are supposed to be connected.

Note 1: The orientation of J28 is different than if you attempt to determine the correct connections directly from the information in the service manual and the circuit board markings. Specifically, the "Balanced Output Schematic" (p# 6-21 of the service manual) in conjunction with the interconnection diagram (p# 6-19) shows that the 'hot' pins of the XLRs go to the pins 3 and 4 of J28 (respectively). This will indeed work, but because of how the output ground is connected, this connection will result in the signal exiting from the XLRs being 180 degrees out of phase with the signals from the mono outs. The diagram shows how to connect J28 so that the XLR output signals have the same phase as the mono outs.

Note 2: While J28 can functionally be flipped one way or another (with only an audio polarity difference), the same isn't true for J27. Pin 3 needs to go to both transformers as a ground reference - so the orientation is important.

{{Side Note - The service manual XLR pin numbering is different than 'normal'. The relative locations are correct, put I'd expect the signal pin directly across from the tab/ground/lock to be labelled pin "3" - not pin "2" (as noted in the schematic).}}

Connection Chroma and expander

Mirko Lüthge [21010245+]

Hi there,

I am owner of a Chroma and Expander (both with MIDI). Both instruments have got a multipin-connection (where the MIDI-Interfaces are connected with). I would like to know if it is possible to connect both instruments directly with a multipin-cable (without MIDI) ?

David Clarke [21030085++]

Yes. If the multipin connection (DB-25 connector) is not being used to provide MIDI, then it can be used to connect a Chroma to another Chroma, a Chroma to an Expander or even a Chroma to a Chroma Polaris.

The necessary pinout for the cable is provided in the Service Manual, page #6-21 [Balanced Output Schematic].

Chris Ryan [21030691]

Am I correct in remembering that this is not the same pinout as in the 25-pin cable supplied with the computer interface kit? I have a vague recollection of that, but I could be wrong.

David Clarke [21030085++]

I'm not familiar with the interface kit cable - but the cable to connect two Chromas together ('Chroma', 'Expander', and/or 'Polaris') is mostly a "crossover" or "flip" cable.

That is to say, the pins designated as 'outputs' from one interface need to be routed to the corresponding 'inputs' on the other machine (and vice versa). Pin 5 is a +5V power pin, and should not be used when two machines are connected (since you'd in effect be connecting the two machines' power supplies together).

Chroma patches help


This is plea to a good Chroma sumaritan. I just replaced my battery on by long in the attic Chroma, and no longer have any patches. I do however have a Atart St and Macintosh computers. Could anyone send me patches for one of those computers ? Help is greatly appreciated in advance.

Chris Ryan [21030691]

There are hundreds of patches--including the factory sets--on the Patch Downloads page at the site.

Patches are available in Galaxy and sysex format. To use the former, of course you'll need a copy of Galaxy. To load sysex patches into your Chroma, you'll need a sysex transfer utility. [See Patch Editors & Librarians: Mac OS.]

Murray Macdonald [21030276+]

Hi Chroma fans...

This problem can be avoided by changing the batteries while the power is turned ON. Sorry this doesn't help you Gene.

chroma repair

Mirko Lüthge [21010245+]


For your information: my chroma expander had been repaired by the company Xtended, Oranienstr. 6, Berlin. It repairs all kinds of analog synths. Another question: I found that my exp. hasnt the same system version like my keyboard, so it isnt possible to transfer all programs from the chroma to the exp at one way (only one program via split 20). In the manual I red that there are two different system version existing (one by which it is not possible to use the last 5 programs). Is it possible to get the best one ?

thanks a lot

David Clarke [21030085++]


I think you are looking for new firmware for the unit. You can find the firmware images at the Chroma EPROM Code page.

The latest Expander images are Rev 14 (the files entitled 14ECBSxx.OBJ).

If you have access to an EPROM programmer you can program the chips yourself. If you do not, then I'm certain the company you had repair your Expander could create them for you.

Chroma For Sale

Rich Davis [21030841]

Rhodes Chroma SN# 21030841 for sale to the best offer.
ROM C8 Rev 14

I bought this Chroma new from a local music store back in 1985. I actually used it little except in my house, it was too big to cart around. It ran fine until about 1989, then it started acting up. Funny characters displayed on the read-out etc. So I parked it in the case and there it has been since. I'm sure it needs a new power supply and work on the dual channel boards.

I have along with the Chroma and the case itself, 2 pedals, a JL Cooper MIDI interface, a cassette tape from Rhodes/CBS with 150 patches, ALL THE MANUALS that ever were put out for the Chroma including The REPAIR manual complete with schematics.

Buyer will pay agreed upon price PLUS actual shipping charges. I will accept payment via PayPal only! This protects both you and I.

Please see [obsolete URL removed] for pictures.

Here is one of them.

For any questions email me at [e-maill address removed]

Jerry Leonard [21030100++]

When does the offer period end?

Rich Davis [21030841]

I haven't put a "time limit" on it per say, just depends on the offers that come in.