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ChromaTalk Archives: April 2011

Expander Performance Manual

Chris Ryan [21030691]

After a dozen years of compiling information for the site, it's not often that a significant new piece of information comes along, particularly something that was produced by CBS/Fender. But recently Eric Mattei [16330105+] brought to my attention the Expander Performance Manual, which is now available on the site. There's a large amount of overlap with the (Chroma) Performance Manual, but there are a few sections, linked from the main page, that provide valuable information on using the Expander. I think this will be of some use to Expander owners, and for all of us provides a rare bit of documentation on this unit.

Thanks to Eric for transcribing the text and adapting the audio mix diagram.

Eric W. Mattei [21030443+]

Thanks to David Clarke [21030085++] for figuring out how the audio mix diagram should be wired. One of the innumerable contributions David has made to the Chroma Community.

Paul DeRocco [21030230]

Gee, even I didn't know this ever existed. My Expander came with Chroma documentation, and even that looked like high quality photocopies: the big foldout cheat sheet that listed the parameter choices in orange boxes was reprinted in B&W.


Thanks to David Clarke for figuring out how the audio mix diagram should be wired. One of the innumerable contributions David has made to the Chroma Community.

Thumbs up on that one!!

CPU Board on eBay

Chris Ryan [21030691]

Item #300542466444, USD$550.00. Description: "Rhodes Chroma Rev 14 CPU Board. Last known to be fully functional."

Picture from the auction:

David Clarke [21030085++]

This version of the board is marked with an ARP logo, and it would be earlier than the CPU board that most of us would have originally gotten in our systems.

The sticker on the lower right hand corner of the board should be covering a 'revision' indication - but assuming this is the same as the ARP CPU board I have here (a gift from Ron Joseph on the Chroma List**) then:

  • it's marked as "Rev 1"
  • the loose wires you see in the picture are "intended" are would need to be attached to the I/O board for proper functioning.
  • there are additional modifications to the back of the board with cuts/straps and components added on.
  • the board is marked with a 1981 copyright (date codes of the chips soldered into the board would also imply build/assembly in early/mid 1981).

I suppose someone might want this board as an oddity - but $550.00 is big price for a 'nostalgia' purchase.

(** Ron - I do still have it as a 'to-do' to do a detailed compare of the old CPU board vs. the later ones - and make that available to the site - but alas, it just hasn't happened yet).

Ron Joseph [21030042+]

I'm still behind on installing a new power supply and two pressure strips; so I totally undertand Dave. What I don't understand is why someone would purchase this rather than the CC+.

Re: a few BCR-2000/alphanumeric display questions

Go to first message in thread, March 2011

David Clarke [21030085++]

... hopefully my LAST question regarding BCR usage:

i have the sysex file for the "B" bank stored in the BCR, but the "B" presets are controlling the "A" bank. is this again, an internal > setting in the chroma that needs to be set? or in the BCR? thanks so much for the help, its really opening up the instrument!

If you can get a MIDI monitor to see what the BCR-2000 is sending for a 'B' bank, then we'll know exactly where we're at. If it is sending a CC which should be a 'B' parameter for the Chroma (for instance), and it seems the Chroma isn't listening to it properly, then we can look to understand why (e.g., that would be a CC+ setting).

If you don't see a CC controller number associated with the B parameters (e.g., if the BCR-2000 isn't sending what was expected), then the question would be back on the BCR side of how its set up.

Perhaps one of the other BCR-2000 users on the list can comment on what is expected from the 'A' and 'B' banks referenced (I don't have a BCR-2000 myself so I can't speak too much about what should happen on that end.)

EQ Board on eBay

David Clarke [21030085++]

Item #300542946621, USD$175.00. Description: "Rhodes Chroma EQ Board. Last know to be working."

This is from the same seller [syntronicsaudio, see] as the older CPU board. While still a high price, assuming the board is actually in good shape then at least if someone bought the EQ board (vs. the CPU board) they might end up with some elements they could reuse (e.g., sliders + CEM3360's).

Picture from the auction:

RJ Krohn [21030455]

EQ Board on eBay (speaking of sliders)

not sure if this helps anyone, but i saw mention of buying an EQ board for the replacement sliders, and figured i'd pass along this tidbit:

i rehabbed a kurzweil midiboard last year that had some of the slider pots broken. i found a replacement value at mouser that actually has a light up LED for the post-the same ones phil cirocco used on that one arp odyssey he redid w/ "christmas light" colors. if memory serves, it was a drop-in replacement. these pots look to be identical to the chroma ones, to me. it definitely looks way cooler than the stock ones with the lights, and are nice and smooth in their throw, not "sticky" or gummy like those old slider pots. if its of interest, i may be able to dig up the part #.

Chromatrol Panel B settings-these working for you guys?

RJ Krohn [21030455]

hi all, so i verified that the file "chromatrolpanelB", as loaded to my behringer bcr2000, seem to output the same CC messages as panel A, per the messages im getting if i feed Osculator with the BCR.

has anyone got the Panel B" file to send the proper messages from their BCR? do i need to "re-map" them manually? (and if so, how?)

thanks for any help

buttons respond, no sound.

Steve Wilson

hello, this community is really great! I have learned a lot from lurking about and checking out all the technical articles and so on.

I do have a few questions. I have read over the diagnosis page, but had a few questions regarding a Chroma I am repairing.

This particular chroma "21030218" has the C++ upgrade, and new power supply.

these were both installed by the customer, but when installing the power supply he said he had some grounds disconnected, or something. and so after installing the supply it does not sound.

The supply points test good.

When the unit is turned on the data readout reads 01234567 same when the the computer is reset.

I assume that this is an error message? it doesn't say ERR though, but I assume its because the display doesnt have enough characters?

I get no output through the main out or through audio outputs 0-4 but the buttons all seem to respond

cr2 and cr1 test good. when I reset the computer I can see a signal on pin 7 of z20, but that quickly goes away.

any thoughts?

Jesper Ödemark [21010135]

When the unit is turned on the data readout reads 01234567 same when the the computer is reset. … any thoughts?

That simply means that all eight voice cards (card 0-7) failed auto tune and was shut off.

Chris Borman [21030194+]

Likely the ADC is blown. Happened to me on two Chromas that I replaced the PSUs. Just get another and make sure ALL the grounds wires are back in place!

Chris Borman [21030194+]

That would be the DAC. Z24, 7541AJN available from Digikey.

Chris Ryan [21030691]

When the unit is turned on the data readout reads 01234567 same when the the computer is reset.

See Performance Manual: Diagnostics - Error Messages. This is in the FAQ. Maybe I should put together a service-specific FAQ.

Luca Sasdelli [21010226]

Hi Steve,

if some ground wires weren't reconnected as required, you can have some instruments parts totally not working. Therefore, before deeping into component troubleshoot, I recommend to make sure that ALL boards are properly connected to PSU. With a DVM you should be able to read the right voltages on Channel Motherboard, I/O board and EQ board. CC+ I guess it does work because you can see come codes on display.

It is mandatory that even the PSU connectors (P1, P2 and P3) are set as per original PSU layout: same connector type, but different pinouts. Service Manual: Disaassembly - Figure 3-5.

Steve Wilson

Thanks for all of the advice!

I did see the ERROR message diagnostics FAQ, but I guess It was the fact that the display doesnt say "ERR" or "E" that confused me. i assumed so, and did check the diagnostics list, but no progress yet.

I did double check the psu connectors, and they are as they should be. (thanks for the tip Luca!) and all the grounds are indeed connected.

I'm going to check out the DAC to make sure that all is well there. Will keep you all posted!

thanks again,

Steve Wilson

ok so replaced the DAC just to be sure, and it is not the problem. checked all the supply voltages on each circuit board. ALL ok.

going off of the common all voices failing problems:

  • The mother board's zero-crossing detector

This seems to be doing its job... upon power up and reset I see a brief square wave on the output of Z20. so that seems good.

  • The mother board's sample and hold decoder

The sample and hold seems to work... SHA0, SHA1 and SHA2 have a brief square wave upon power up and reset. and the outputs of Z8 a and b have some pulse waves on them... but they don't change when I press keys or anything.

  • The mother board's data strobe decoders

what should I see with these?

  • The I/O board's pre-set potentiometer R1

I have set this, and it's good.

  • The I/O board's capacitor C31

I could not locate C31, but the 2M clock is there, so I assume all is well?

  • A voice board not being silent when another board is being tuned

not sure if this is happening or not, if I pull all but one voice card will I be able to tell?

Thanks guys, this is a monster and I really appreicate the help of people a bit more familiar with it!

Paul DeRocco [21030230]

Another useful tool is to use SET SPLIT 31 to force the Chroma to enable all the boards even if it was unsuccessful tuning them. The tuning parameters on failed boards will be set to reasonable defaults, so the boards ought to make some noise. You can then make sure that the analog channel controls (pitch, width, cutoff, volume) can be varied, and that the digital channel controls (patch, resonance, wave shape, output select, sync, ring mod, filter FM) can be changed. That covers a lot.

But it's still most likely that the problem is in some circuit common to all boards. Follow the SYNTH ZCD signal into the digital circuitry that measures its period, and see where that leads you. Most of that circuitry is shared with the cassette, so whether or not you can load a program from the cassette could be a useful clue.

Steve Wilson

[Duplicate of Steve's email above of Fri, 8 Apr 2011 22:47:53 -0700]

Paul DeRocco [21030230]

Isn't this a repeat of your post of two days ago? Anything new?

Steve Wilson

sorry, i reposted because I wasn't sure if the original post got lost amongst the ebay excitement.

don't have any updates at the moment.

Heinz Weierhorst [21010276]

Hi Steve.

Try to isolate the voice that is not silent while autotuning. Then remove it and check again.

Expander on eBay

Chris Ryan [21030691]

Item #180650545929, starting bid USD$4,500.00 (or "buy it now" price of USD$7,800.00), no bids yet, ends April 10. Has a fan, and the owner cut an air intake hole in the bottom of the unit. And he has "completely rebuilt the power supply. C3 is now 50,000ufd 16VDC rated allowing me to remove the OverVoltage Crowbar circuit and all Series Pass elements have been replaced as well as the rectifiers and electrolytic capacitors. The capacitors have been replaced with 105 degree Panasonic FC or Nichicon types with higher microfarad values. The Dual Channel Voice Card Motherboard has been upgraded as well. The batteries have been replaced with rechargable Li-ion types and the battery holder was replaced as well." Also has an internally installed Syntech MIDI interface.

"Everything works really well. All diagnostics pass and tuning is stable. I am attempting to recover program tapes from 1989 and get the unit sounding like it did then. If that fails, it will be loaded with a bank of programs from several friends here in LA."

This is Expander 16330120, new to the registry.

Chris Ryan [21030691]

Re-listed as Item #180652843007, starting bid USD$6,800.00, no bids yet, ends April 21.

Chris Ryan [21030691]

Re-listed again as Item #180657822922, starting bid USD$5,800.00, no bids yet, ends April 26.

Go to next message in thread, July 2011

Advance Planning for Next CC+ Batch

David Clarke [21030085++]

The CC+ systems are generally built either by myself or Mr. Sandro Sfregola [21010294]. To help keep shipping and duty costs lower, we normally split up orders by geographical location with me generally looking after North, Central and South America, Australia, China and Japan. Sandro (in Italy) looks after Europe, Africa and the Middle East.

A European build is nearing completion, and Sandro's 'wait list' is essential empty - but there are members in the areas that I look after currently looking for boards.

Based on our personal schedules and the status of the 'wait list', the build currently underway in Italy is planned to be the last European-based build for 2011.

I am planning to make another build of CC+ units this year - but once that is complete, that too will likely be the last CC+ build in 2011.

I will plan to send another notice to the list once firm dates for the next build are set; however, if you'd like to get a CC+ in 2011 (and haven't already been in touch), please let us know so we can consider you in our planning.

Thank you for your continued interest and participation.

Chroma Dual Ch Boards on eBay (not mine)

Sandro Traversi [21010217]

[eBay item #180634010996] Pictures from the auction:

Re: CPS Kit

Go to first message in thread, April 2011

Enrico Dibennardo [21030494]

Hi Chris, I sent the payment last week, please confirm me that you received it. Thanks.

Chris Borman [21030194+]

Hi Enrico,

Yes your payment was recieved, thank you Enrico! The PCBs are in and the long lead FSRs are due to ship this Friday. Three folks left to submit payment that are needed to order the remaining parts.

RJ Krohn [21030455]

thanks so much, chris for doing this! its truly special; i can't think of any other vintage synth that it would even be possible to find folks to provide this kind of support (no one wouldnt even consider the possibility to get an aftermarket AT kit made for anything SCI/Oberheim/etc). lets get this thing knocked out, folks!!! im excited!!!

midi interface on

Jesper Ödemark [21010135]

A couple of interesting interior shots if anyone is interested. [Item #260766555256]

This is a JLCooper ChromaFace. Picture from the auction:

Chris Ryan [21030691]

A couple of interesting interior shots if anyone is interested.

Those pictures are deep linked from the ChromaFace Manual at the site. :)

Jesper Ödemark [21010135]

Oups... OK. :)

The poor man's chroma enabler

RJ Krohn [21030455]

hey all, thought i'd post this pic of my new setup. [See for comparison Randel Osborne's [21030467] Chroma Enabler] it's just two bcr 2000's w/ wood end cheeks i made, overlays, and a simple hinge/support on the back so that they stand up for easier access. it really is quite comfortable-i dont have to bend over, it's all up front and comfortable to see, and the second unit allows me to not switch back and forth. i'm gonna try to find a big version of the parameter chart to print out, so i know what is what on some of the encoders.

oh, as an aside-i notice something kind of odd on my chroma. its not uncommon for one voice to fail autotune. but it's ALWAYS an odd voice. "err" 1,3,5, or 7. (i know these are actually 2,4,6, and 8 but whatever). this is about 50% of the time, so it's not a huge deal, but just thought it was bizarre. maybe one side of a logic IC on the MB has a slight fault?

Chris Ryan [21030691]

i'm gonna try to find a big version of the parameter chart to print out, so i know what is what on some of the encoders.

The Parameter Chart is available in PDF so you can print it as large as you want.

RJ Krohn [21030455]

thanks chris-i actually sent the file to my local printer, and they said that because of the size of the file, as soon as it goes over 9"x21", it will lose resolution. but maybe they were BS-ing me? the one i pulled is an 82kb PDF off the site. thanks for any leads, maybe i pulled the wrong PDF off the site?


Wait, im a poor musician and father with a college student and have a Enabler, doesnt compute lol

Chris Ryan [21030691]

thanks chris-i actually sent the file to my local printer, and they said that because of the size of the file, as soon as it goes over 9"x21", it will lose resolution. but maybe they were BS-ing me? the one i pulled is an 82kb PDF off the site. thanks for any leads, maybe i pulled the wrong PDF off the site?

I am not a print expert but PDFs are resolution independent and you should be able to create a parameter chart billboard from the file if you wanted to. File size doesn't come into it as they're just mathematical descriptions of shapes, which are output at the printer's resolution.

RJ Krohn [21030455]

Wait, im a poor musician and father with a college student and have a Enabler, doesnt compute lol

haha, as a disclaimer, i STILL want an enabler! i still have to visualize "flow chart" in my mind, so its still pretty non-enabling, but better than one slider and some membrane buttons(how did those cavemen do it?!?!?!?!) :)

James Coplin [16330036+]

I am not a print expert but PDFs are resolution independent and you should be able to create a parameter chart billboard from the file if you wanted to. File size doesn't come into it as they're just mathematical descriptions of shapes, which are output at the printer's resolution.

Not necessarily. You can embed any standard graphic format into PDF vector *or* raster. PDF doesn't magically convert the raster into a vector format – it just embeds it. If the chart is a vector format native and then put into PDF, you can resize at will. If the chart is raster originally, it is still raster. If it is a scan into a PDF, it actually will still be a raster unless you ran the optimizer in which case Acrobat will attempt to convert what it can to vector and leave the rest as a raster.

Chris Ryan [21030691]

Yes, the parameter chart is all vector graphics. I drew it from scratch in OmniGraffle.

James Coplin [16330036+]

In that case, you should be able to wallpaper your house with it. Wait a minute

Chris Borman [21030194+]

My Son tries out for JV Football this year. Think I'll use the link to make him a Fathead!

Chris Smalt [21010280+]

but better than one slider and some membrane buttons (how did those cavemen do it?!?!?!?!) :)

Well, I'm one of those cavemen, and in my experience the Chroma was a very fast synth to program, once I got the modulation sources list in my head, which took a couple of weeks. I was happy with the large size of the membrane switches, and the tactile feedback from the tapper. I loved being able to adjust all parameters without moving my left hand, and the slider position actually gave good visual and tactile feedback of the current value. The display mainly served to check mod sources. Don't forget other synths of the day with a data slider had tiny buttons, and displays that were hard to read from the player's position.

For live performance I relied heavily on the two swell pedals and the parameter slider.

Rhodes Chroma For Sale 21030880

Paul Thompson [21030880]

Everyone- Ok Chroma #21030880 is now up for sale as I promised last month. You can see photos.

First off- I'm not a musician or a service technician so I had a professional technician examine this unit and he found that the power supply needed a couple of capacitors before he could further diagnose the unit. This Chroma powers on and all of the LEDs light up. It has a hum as it powers on. I have elected to sell it as is rather than chase my tail diagnosing/repairing at $50 an hour plus parts. This Chroma was kept stored in a climate controlled indoor storage unit and is in very nice condition. The technician feels that this is definitely a repairable Chroma- not one to be parted out. It comes with two foot pedals (see photos).

This Chroma comes with the original Anvil case which I have largely stripped of the rotted foam- it will need to be re-foamed. The case is in very nice condition. I did very carefully clean all of the foam rot off of the Chroma and I have completely refinished all of the wood with a very nice flat varnish. The unit is in overall very nice condition as you can tell from the photos. There is one indentation in the wood on the left side panel and one small scuff on the black top panel. The keys are all super clean and operate cleanly and smoothly.

I'd like to sell this Chroma through the Rhodes Chroma website rather than going on Ebay. If I can do that I'll make a fair donation to the website. Please feel free to direct all offers and questions to me. Please keep in mind I'm selling this Chroma AS IS and it will be up to you to make it stage ready. I will pack and ship this unit virtually anywhere with insurance. Please provide a shipping address with your max offer and I will promptly reply with a shipping quote. If I can't get what I feel is a fair price than I'll list it on ebay. I will only accept PayPal or cash as payment and of course local pickup is always available- I'm in the Dover, DE area. Thanks everyone....

Doug Terrebonne [21030114]

What do you consider a fair price?

Paul Thompson [21030880]

Right now I'm taking offers on this Chroma and to a certain degree fair market value will be determined by the Chroma community or Ebay community. A Chroma sold a few weeks ago on ebay for $2,410 that exhibited the same behavior as mine. The cabinet looked very rough compared to mine which has been completely refinished. I'm also including two foot pedals and the Anvil case. I won't be offended by any offer but I would use recent sales as a barometer. I can arrange personal delivery within a 150 mile radius of Dover, DE for a small fee.

Mark A. Lange [21030459+]

Well.... IMHO, an eBay sale will cost you $$ and then there's the potential liability in dealing with fraud. Plus stress... and the ever-present hassle factor. Perhaps you should consider a minimum acceptable price and let us know. This would yield a potential buyer without turning the Board into an auction site. And for the record, I am not interested in buying a third Chroma at this time. :)

Paul Thompson [21030880]

Mark- Fair enough on not turning the message board into an auction site, however, I certainly think the members overall would be appreciative that I'm giving first crack to the message board community and not going the ebay route right away. I'd rather make a donation to the Rhodes Chroma website than pay the listing and final value fees on ebay. I've already had a few good offers but if I could be in the $2200-$2500 range (plus shipping) I'd be more inclined to sell right away. Thanks for all the interest....

Chris Ryan [21030691]

I'm fine with using the list this way—one might be tempted to say, particularly if donations are forthcoming, but it's more that Chromas sold here will probably go through a more fair sale process (e.g. avoiding the last-minute bidding frenzy that one often sees on eBay), and perhaps more importantly go to a good home. The list has been higher volume in the last year or so but I've only seen a couple of people switch to digest format.

Paul Thompson [21030880]

21030880 Up For Sale on Ebay

Everyone- based on initial response from the message board I've decided to list Chroma 21030880 on ebay. The listing should go up tonight (Wed. night). Thanks to everyone for your interest. I'll keep you updated or I'm sure Chris will keep you updated.

Chris Ryan [21030691]

Re: 21030880 Up For Sale on Ebay

Item #220773010042, starting bid USD$995.00 (reserve not met), ends April 25.

Chris Ryan [21030691]

Re: 21030880 Up For Sale on Ebay

Sold for USD$2,272.00.

Cps kit Update

Chris Borman [21030194+]

Folks, the PCBs and FSRs are in. I am waiting on three remaining payments to cover the rest of the parts I need to order to finish the CPS Kits.

RJ Krohn [21030455]

thanks chris-is there anything those of us who have paid do to help the project along? anything else we can provide? thanks again for doing this.

Chris Borman [21030194+]

I just sent reminders this morning. A few folks wanted to defer payment, which was fine, but with the long lead items having been received, its time to complete this build for you guys. Just need to collect the rest of the cash to fund purchase of the remaining parts.

Polaris on eBay

Patrik Gudmundsäter [21010240]

There is a seemingly nice Polaris at Ebay right now.

Chris Ryan [21030691]

Item #140536279226, ends April 26, current bid USD$217.50. Sounds like it has a few issues.

Doug Terrebonne [21030114]

Wow it's been bid up to $500 already. In the Q&A the seller reveals that not all the buttons are working so I hope the bidders realize 1 or more of the ribbon cables are broken...

Chris Ryan [21030691]

Sold for USD$611.00.

Drehbank on Ebay for CC+ users

Jesper Ödemark [21010135]

Hi list,

I wanted to mention this auction if anyone is interested in the Doepfer Drehbank to go with the CC+. [Item #290557113395.]

My template with the settings can be found on the site.