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ChromaTalk Archives: September 2006

Parameter Chart Update

Chris Ryan [21030691] · Fri, 1 Sep 2006 07:49:53 -0700

Åke Danielson [21010068] has provided an update of the Parameter Chart to include CPU Plus (CC+) functions. Thanks Åke!

Jesper Ödemark [21010135] · Fri, 1 Sep 2006 17:28:43 +0200

Cool!

Is Åke another swede? I cannot really imagine anyone else named like that. ;) Anyway... I'll print that on the double.

Åke Danielson [21010068] · Sat, 2 Sep 2006 00:25:03 +0200

Of course I'm a swede. Were else could you get a weird name like that!!!!!

Jesper Ödemark [21010135] · Sat, 2 Sep 2006 12:30:01 +0200

Cool!

There seems to surface a lot of Chromas up here among the icebergs (pun intended!) [Åke's e-mail address includes "iceberg"]. But you mail address says Netherlands... anyway, good job on the chart!

Martin Straw's PS modifications

Tom Moravansky [21030431] · Sat, 2 Sep 2006 19:57:58 -0700

Hello - I'm going through my Chroma and decided that since all voices are now working and the CC+ board is working, it's time to do the PS modifications.

One main question before I get too far -- in Section 3.1.3 of Martin's document, he mentions that some Chroma PS boards were modified at the factory in a way that invalidates the F1, F2, and F3 connections. However, no mention is made of how to determine if you have one of those factory modified power supply boards.

Anyone have any additional insights here?

Tom Moravansky [21030431] · Wed, 13 Sep 2006 16:25:08 -0400

Martin Straw's power supply update procedures

Chroma power supply upgrade.

Since my Chroma was mostly apart to fix all the battery leak damage, I decided to give Martin Straw's power supply upgrade a whirl. His on-line document is a great resource for what to do, but it doesn't really cover *how* to do it. What I'm going to attempt here is to try and convey what's really involved and what you'll really need to do, as well as pass along other tidbits I came across in the process.

First - the Chroma power supply board has large traces and large ground planes. If you don't have a good temperature controlled soldering iron (and desoldering iron) you probably shouldn't attempt any of this work. I ended up using both a desoldering iron and a manual vacuum pump desolderer to clean out the holes and remove components (I used the manual one for the large stuff to avoid clogging up my desoldering iron).

Next - if you decide to do this mod, make sure you purchase all the parts you'll need before you start. There's nothing worse than getting 3/4 of the way through it only to discover that you don't have any 9.1k resistors in stock and it is 11:30 at night on a Saturday. One thing I did that wasn't in his document is to replace all the electrolytics (except the large C3 cap) while I had the PS out and apart. Since heat is a big enemy of electrolytics, it made sense to me to replace them at this time. One side effect of replacing the caps is that there was negligible ripple in the supply to C3. I had a tough time seeing any bump on my scope and the Fluke 8060A meter was rock steady out to 2 places. The third position after the decimal would sometimes toggle between 2 numbers (i.e. - 6.456 to 6.457).

OK - you decided to do the work. First, get the power supply out of the Chroma. I would do this mod before installing the CC+ MIDI ribbon cable in the back panel (I ended up taking that ribbon off) because you want to have the PS completely free of the Chroma. Next, unhook the cables from either the power supply or the connecting boards (in the case of the back panel jacks). Have a Sharpie ready to label every cable and its orientation if necessary! I cannot stress this enough. Don't rely on your memory. Don't rely on the service manual. Label it. Next, unhook all the connecting ground cables. Remember to save the screws, lock washers, and standoffs. The service manual says there are 10 screws on the bottom that need to be removed to get the power supply out. On my Chroma there were only 8 (screws #5 and #6 were not there). The other two were inserted from the power supply board top down into the base. Look at your PS board carefully. If there are screws there on the top, remove those first, then flip the Chroma over and remove the other 8.

Once the PS is free from the Chroma always carry/move it with 2 hands. One hand should be on/under the transformer and the other supporting the metal heat sink/backplane. I did things in a certain order. You may decide you want to do it differently. One thing I would caution though - solder in the regulators last. The reason is that you will constantly be handling the PS assembly and turning it over, standing it on end, drilling holes in it, etc, etc. The back plane and circuit board will flex slightly, putting pressure on the regulator legs and the solder joints. Excessive amounts of flex will cause cracks and bad connections. This should be avoided. So, install the regulators last.

More parts notes - at least in the States, the IRF531 is no longer readily available. However, the NTE66 is a proper substitute (and expensive too). Another thing you'll need - heat sink compound. Talk to your local PC hot rodder to see if they have any or stop by an electronics store like Radio Shack or a computer store like CompUSA, or order it from Mouser when you order the other parts. If you break or lose the insulator tabs and small plastic rings, you'll need to replace those. Shorting out the regulators against the frame is a very bad idea. When you are ordering parts, it's a good idea to order 1 or 2 extra, just in case. Trust me - the shipping charges on a second order will be more than the cost of a couple extra resistors or ICs.

Still more parts notes - the suggested 4 watt 1 Ohm resistors are hard to find. Measure the length of the existing resistors (R26 and R31) and look for some 5 watt ones of comparable size. There is a wide size variation. If you get resistors that are too large, they won't easily fit in the location.

Final parts notes - I didn't buy the wire wrap sockets as mentioned. I've had bad experiences (literally) getting the square pegs into the round holes without damaging the through hole plating. I know each circuit board is different, but I didn't want to chance it, so I bought some 'long tail' solder sockets. If you do a search at Mouser for long solder tail socket, you should get a hit. They provided additional clearance and allow airflow under the IC as well as providing extra metal in the leg height for heat dissipation.

Some of the components were hard to get out because of things in the way. Especially problematic was Q5 which in my machine was jammed right up against the large C3 support bracket. If you unsolder some of the transistors and the resistors mentioned, it makes it a bit easier to get to the 2 LM 358 ICs. Don't even bother trying to extract those neatly. Clip the legs off, throw away the IC body, and then use needle nose pliers and your soldering iron to extract each leg. Remember that they were probably bent over on the underside, so a little prep work with a small screwdriver and a solder vacuum may make it easier.

Daughterboard - I used a small board from Radio Shack. It's a plain small perforated square. It came as two boards lightly joined together. I mounted one trim pot in the upper left and the other in the lower right. My resistors came out at right angles from the trim pots. Instead of using some type of L bracket, I simply used 2 old board standoffs. If you've ever cannibalized an OB-X/Xa/8 you'll have a lot on hand. Otherwise, order a few with your parts. I measured and drilled 2 holes in the back, near the serial number label. I used screws and lock washers to mount the board to the Chroma back. I soldered the wires from the PS first and then cut them to length and soldered them to the daughterboard second. In retrospect, I think I'd do it the other way around next time. I used 26 gauge wire because that's what I had available. I may revisit that and use 24 or 22 gauge before closing up the Chroma.

After replacing the regulators, I completely defluxed the back of the PS and scrubbed it with a toothbrush. Then I took a low power magnifying glass and looked over everything carefully before applying power. This is your Chroma PS after all and you'd hate to blow it up by being careless at the end. I used a multi-meter to verify I had no regulator shorts against the ground plane. Note that depending on your multi-meter and they setting, you may register continuity in a couple surprising places because there's only a 100 ohm resistor in the path. Decrease your range and retest.

Recheck all your wiring to and from the daughterboard. Verify you don't have any solder bridges. Verify you can get to the trim pots when the board is mounted w/o electrocuting yourself.

Next, I powered up the PS without hooking it to the Chroma. Please note - since I neglected to verify the trimpot setting for the pre-regulator circuit, I blew my 1A fuse (have some on hand) before I could trim it down. Basically the crowbar overvoltage protector did its job and saved the capacitor. Before you power up - hook up your multi-meter to the wires going to C3 and set the range to cover 5 to 8 volts. Have your trimmer tool in one hand in the trimpot slot and have the trimpot in the middle of its travel. Flip on the power switch and make sure you trim the voltage to stay below 7 volts. Once it stabilizes, then you can tweak it as recommended in Martin's document.

The +/- 12 volt trimmer trims the -12 side. First measure the +12 side and note the voltage. Now, while measuring the -12, trim it to match the +12. I let my PS burn in for an hour the first day. I plan on letting it go for 4 to 6 hours and then checking for any hot spots before putting it back in the Chroma and then retesting.

Hope that helps someone.

Chroma on eBay

Chris Ryan [21030691] · Fri, 8 Sep 2006 07:29:51 -0700

Item #200025067803. From the UK. Current bid £103.00; apparently no reserve. From the description: "You're looking at a Rhodes Chroma in mint condition. You will find it very hard to get a better one than this. It comes with a recent full service in which the whole unit was electronically tested form top to bottom. All the electronics are working perfectly and it sounds amazing. ... This Chroma is fitted with Midi and this can be used to load or dump patches and settings." Not sure whether this instrument is in the registry; I've contacted the seller.

Paul Hackett-Evans [21010094] · Sat, 9 Sep 2006 02:10:42 +0100

Chroma for sale on Ebay UK

Not mine!

See Ebay item number 200025067803

The Chroma looks modified there are 3 MIDI sockets riveted to the back panel in the cutout next to the computer interface, plus two momentary pushbuttons drilled into the rear panel next to the Write Protect switch. [Here are pictures from the auction:]

Physically it looks in nice condition, the wood seems nice.

The ad says:

Rhodes Chroma - Unbeatable quality

You're looking at a Rhodes Chroma in mint condition. You will find it very hard to get a better one than this. It comes with a recent full service in which the whole unit was electronically tested form top to bottom. All the electronics are working perfectly and it sounds amazing.

The Chroma was originally developed by ARP who were subsequently taken over by CBS Fender who added the synth to the Rhodes family of Keyboard instruments. As a result it has some classic ARP style sounds in the style of the Oddesy etc, but with the playability of a real instrument like the Rhodes electric pianos. This is a true keyboard players instrument, well designed for performance.

I can't personally think of another analogue synth that has this many oscillators. The polyphony is fantastic and it can be used to make the most beautiful string, synth and pad sounds as well as huge basses and leads.

This Chroma is fitted with Midi and this can be used to load or dump patches and settings. You can also connect the Chroma to an Apple II computer for advanced editing. These can be acquired on ebay for next to nothing.

If you want any further information about the Chroma then please visit the following websites:

Caveat Emptor

This Chroma is fully serviced and fully operational. I will ensure that it is delivered in full working order. It is however a 20 year old instrument. As any serious buyer will know, Vintgae Synths can require regular maintenance. I will therefore not be able to accept any complaint about the synth becoming faulty in 12 months time etc.

Included in this auction are the following items:

  • Original Volume Pedal
  • Original Foot Pedals
  • Original Footswitch
  • Full Flight Case
  • Photocopied (sorry) manuals
  • The Rhodes Chroma itself...obviously

I've emailed the seller to ask the serial number, who serviced it and what was done, also what the switches on the rear panel are for.

Jesper Ödemark [21010135] · Sat, 9 Sep 2006 09:49:11 +0200

Re: Chroma for sale on Ebay UK

Sounds like a Kenton midification...

See Drawing 5 in the Kenton documentation.

Rob Belcher [16330123] [21030095] · Sat, 09 Sep 2006 10:58:13 +0100

Re: Chroma for sale on Ebay UK

Hiya peeps,

Im pretty sure thats Ryans Chroma, that is Ryan from Jarberry Music. I would guess its one of Philip Taysom instruments. Ryan has been selling off all of Philips gear over the last year or too...

Chris Ryan [21030691] · Sat, 9 Sep 2006 08:51:58 -0700

Re: Chroma for sale on Ebay UK

I heard back from the seller. This is Chroma #21010104, already in the registry and for sale in April on eBay (the sale fell through). The discoloured key has been replaced, and two voice boards have been repaired.

Chroma 21010022 for sale on eBay

Chris Ryan [21030691] · Thu, 14 Sep 2006 22:16:54 -0700

Peter Forrest (The A-Z of Analogue Synthesizers) e-mailed to let me know that Chroma 21010022, previously for sale on VEMIA back in March, is now on eBay. Item #260031599700, ends September 21, starting bid £1500. From Peter's description:

Very rare - one of only fifty made by the original ARP team who had designed this beautiful instrument ... This particular machine lives up to all the hype about those first 50. It sounds totally gorgeous - rich, powerful, and all of course controlled by one of the best keyboards in the world. Wooden, beautifully weighted, and much nicer than the CS-80. (Of course it doesn't have the rare optional polyphonic aftertouch sensor, and it would be lovely to know if those are possible to find or reproduce.)

It has been fully serviced within the last 8 weeks by Roy Paynter, who is the UK's number one Chroma service guy, and universally recommended. He has a Chroma permanently in his workshop as a test-bed, and knows the machines inside out. His servicing warranty is three months, so there will be ample time for you to check the Chroma out within the warranty period.

This machine must be even rarer than most of the first batch, as it is European voltage. It was originally bought by Ken Freeman, famous inventor of the String Machine, who used it extensively in his music. He eventually sold it in 1994 at the first VEMIA auction, where it was bought for £2000 by Global Communications (Mark Pritchard and Tom Middleton). They then used it in their music for years, but Mark has now emigrated to Australia, and the Chroma was one thing that he couldn't fit into his suitcase.

It is in decent cosmetic condition - see the photos. A very reasonable 7/10, with some little knocks to the wood, and a few minor blemishes. The wood could easily be re-finished for certain, as it's solid..... but who knows if that's the right thing to do?

Comes with all the original literature - the Programming Manual, Performance Manual, Interface Manual, fold-out four side parameter map, and, best of all, the original preliminary Service Manual, complete with all schematics with ARP logos.

I run the VEMIA online auction (Vintage Electric Musical Instrument Auctions). But the owner needs to sell now.... so here this is on eBay. (The next VEMIA auction isn't until November 4-11.) We are expert shippers at decent prices - please look at my feedback.

Chris Ryan [21030691] · Sat, 16 Sep 2006 13:45:46 -0700

Peter has reduced the price based on advice that this may not be one of the first fifty Chromas. He seems to have heard that 2101 models "came after" 2103 and that the first fifty had no vents in the top panel, and had all ARP voice boards. Is this true? (He also points out that the Chroma for sale has flat-head screws on top, while the #21010096 has cross-heads--all original screws.) I'm not sure we've ever definitely defined what might identify one of the instruments "hand built" by the ARP team. This goes back to the debate about how many Chromas were made, and whether there were any serial number overlaps between models [1]. Which there seem to be in the first fifty: 21010006 and 2104006; and 21030016 and 21040016.

Peter writes:

I have been doing a bit of reading on the site, and noticed that one guy visited the factory and saw a load of Chromas including some with ARP logos. Maybe this explains why some at least of the early 50 have ARP circuit boards. Quite possibly the top sections without vents could have come from those ARP machines too. They may have had some new boards made, but also had a bunch of ARP boards to use up.

What I can't get my head around is how the serial numbers were allocated. If they made a decision to make, say, five US models and 2 European models, and started work on more than one at once, at what stage was the serial number allocated? If two were close to that stage at the same time, you can imagine that both could have been allotted the same serial number by mistake. So maybe your original thesis still holds...

I can't imagine they would have made 50 for the US market before starting on any for Europe.

But I note that at least some of the definitely early machines have a serial number which looks more primitive and early than the 0022 one.

I am very confused!!

Paul Hackett-Evans [21010094] · Sat, 16 Sep 2006 22:12:15 +0100

I believe this was one of the Chromas I saw at Roy Paynter's workshop last time I was there. It wasn't in wonderful cosmetic condition, but it was shaping up very nicely as a working instrument and Roy was pleased with how it was going.

If I had this Chroma, I'd probably refinish the woodwork. Regardless of the question-mark over it being one of the first 50 or not, it's a nice Chroma and I think the starting price is reasonable.

I'd buy it if I had the money.

David Clarke [21030085++] · Sat, 16 Sep 2006 18:29:01 -0400

Re: Chroma 21010022 for sale on eBay (how many Chromas)

I used to think they had probably numbered all Chroma's sequentially, regardless of 'model'; however, as the duplicate numbers were verified I came to believe that they likely started afresh with each model.

As possible evidence to this, the field change notices initially only reference the 2103 model - and only the later/last ones talk about models other than 2103. This may tend to imply that a good number of the 2103 models were made before the others.

I too agree that it's unlikely that oodles and oodles of Chromas were made for North America before any were made for overseas - but as the differences between the models are very slight (e.g., minor changes to the power supply, and internal voltage switch), I'd hazard a guess that the 'first' European models may just have been manually adjusted North American versions.

While not perfect (and while not easy to do by all) one method to get a rough timeline of creation would be to look at the date code on top of the integrated circuits associated with the power supply (we'd use the power supply here as the serial number tag is physically attached to it, and so there'd be a higher degree of confidence that the parts match the serial number). If the part(s) look like they were never changed (i.e., the ones installed at the factory), then the date code would at least give guidance as to the earliest possible date it could have been made (for instance - a part dated May 1982 would mean that the power supply couldn't have been made in December 1981, etc.)

If you assume that improvements were made over the course of the instrument, then with regard to tops, you'd generally expect that the ones without vents to be older than the ones with vents - and the ones with vents and mounting posts (for a fan) to be newer than the ones just with vents without mounting posts.

Tom Klepacki [21030025] · Sat, 16 Sep 2006 19:01:47 -0400

Hi all,

My Chroma #25 (I write down the serial numbers of all my gear...) was sold to me with an ARP logo, and a top cover without vents. When I took it to Woburn for servicing, they automatically removed the ARP logo and screwed on a Rhodes logo. I should have demanded the ARP logo back in my hand. They also had identified an excessive heat problem, and the top cover was changed out in a similar fashion, automatically, in an effort to cool the damn thing down. Boy, they ran hot! (My power supply DID burn itself up, in 1985.) Also, if memory serves, they also upgraded the programming, say, from v1.0, to v1.1 Something like that. (I think that is documented inside the case...)

My Chroma still sits in it's Anvil case, unchecked for nearly 13 years. Ouch! I will one day soon get the Rhodes 73 piano off the top of it, move the Wurly 200 out of the way, and open the case. I'll then identify my serial number/ PC boards/ key color, etc. for the Chroma site.

Paul Hackett-Evans [21010094] · Sun, 17 Sep 2006 00:25:45 +0100

Hi Tom,

I hope the batteries aren't still in it after 13 years. You might have a problem if they've leaked.

Jesper Ödemark [21010135] · Sun, 17 Sep 2006 07:09:15 +0200

Re: Chroma 21010022 for sale on eBay (how many Chromas)

So... let all who change to CC+ send in their "IC-codes". If I understood Matthias Becker right, my CPU is already exchanged, but I'll have a closer look when I've upgraded to the CC+.

p.s. Why "1" for Europe and "3" for North America? d.s.

Jesper Ödemark [21010135] · Sun, 17 Sep 2006 07:10:47 +0200

I hope the batteries aren't still in it after 13 years. You might have a problem if they've leaked.

Tom - do that NOW... the list don't want to hear about such behaviour! ;)

Ron Joseph [21030042+] · Sun, 17 Sep 2006 05:16:13 +0000

Hi all,

I'm the source of Peters information. I had contacted him off list in order to leave the matter private if he wanted to. Also, knowing of Peter, I thought maybe I was wrong and the mystery of the first "50" Chromas would get deeper. Currently I'm still of the opinion that the first 50 were all the 2103's. I've outlined my opinions on the site but I'll recap.

The two Chromas I own have, 21030042 & 21030052, the following similarities:

  1. Poly/Mono for parameter 2 rather than FSW
  2. All white ARP boards for voice cards and all other boards in the machine CPU etc.
  3. Discolored keys w/ the highest key being a bold white (no discoloration)
  4. No heating vents on top

John Leimseider [21030434++] told me that 21030023 also had the same keyboard issue and that the new owner wanted it replaced, which John did w/ a later model Chroma.

Personally I think multiple types of boards on the first 50 would seem to be reaching a bit. The white boards are definitely cruder than the following series w/ several modifications being listed in the various tech documents. One of my Chromas had the mods done, one did not.

The white boards are the oldest and my 2 Chromas are late in the group of 50 so why would my boards all be white while other original 50 be a more advanced voiceboard?

My theory is that the first 50 were done as a way to have the team up to snuff so that they'd have some experience w/ the machine before they went to Gulbransen. They used the same distributor as they'd always done so the color of the boards were the same. When they transitioned to Gulbranson they used a different supplier. This also applies to the keyboard.

Also, the first Field change notice gives a list of serial #'s that is exactly 50. 21030011-21030060. This would seem to be a huge coincidence if it doesn't actually mean the first fifty Chromas. As I stated before this would make sense as the first modifications would apply to the earliest models. The 2101 series isn't mentioned until FCN3-008.

The only Chromas I wasn't sure about were the 001A at Dave Hillel's museum and the Halloween Chroma [21030620].

As an interesting aside, there are several serial #'s missing from the later service notes. These are all after the first 50. The problems w/ Gulbranson and the screw ups concerning the manufacture are well noted w/ several former techs saying that machines started coming back to the factory. A guess is that these Chromas were taken apart for workable material when the problem w/ the boards couldn't be repaired.The serial #'s were then scratched off the list as they no longer existed.

So far I've established consistency across the 2103 series for the first 50 w/ 3 machines.The 2101's, even in the early serial #s tend to have similarities w/ later model 2103's.

However, I'd love to hear any contrary opinions as well as from other Chroma owners, especially owners of serial 3s up to 60 on all model #s.........Ron

Jesper Ödemark [21010135] · Sun, 17 Sep 2006 07:47:56 +0200

Your investigation with coclusions sound very reasonable to me!

David Clarke [21030085++] · Sun, 17 Sep 2006 11:29:44 -0400

Re: Chroma 21010022 for sale on eBay (how many Chromas)

p.s. Why "1" for Europe and "3" for North America? d.s.

I think this would be a question which predates the Chroma quite a bit, and goes back to what ARP did or didn't do for serial numbers.

If you look back at other ARP models, you'll generally see that most/all synths (2600, Omni, Omni II, Odyssey, Quadra, etc) all came with 4-digit model numbers and 4-digit serial numbers, very similar to the structure used for the Chroma.

For example, the Omni II Service Manual Refers to Models 2471, 2472, 2473 and 2475 - and all of the internal schematics actually reference "Model 2470" (presumably the "0" the last digit indicates that the material is good for all models - sort of like saying Model 247x).

Here's some of what you might see:

2600 Model 2600-2606
Odyssey-II Model 2810-2813
  Model 2820-2823
4-Voice Model 3351, 3353
Quartet Model 2493
Omni I Model 2480 (but a Field Change Notice Rferences model 2483)
Omni II Models 2471, 2472, 2473 and 2475
Chroma Models 2101-2104
Expander Models 1631, 1633

So - it looks like the model number structure used by the Chroma has been around for a long time.

Perhaps an ARP-tech would have some internal documents or memories of exactly the significance/designation assigned to the last digit of the number.

Based on what we've seen with the Chroma (and the other models), the ...3 does seem to be North America and the ...1 does seem to be Europe.

Ron Joseph [21030042+] · Sun, 17 Sep 2006 16:04:33 +0000

Re: Chroma 21010022 for sale on eBay (how many Chromas)

I was wondering about Peter's valid point that why would they make hundreds of Chromas for the US market before releasing Chromas for the European market?

Perhaps it wasn't planned that way. During that third run of Chromas 21030116? > was when Gulbrenson [sic] had the problem w/ the voice cards. Somewhere on the site someone who worked there said that they started coming back almost immediately and that many machines were lost. If the release of the European models coincided w/ this Problem perhaps they decided not to ship until they fixed the problem. If I was a manager I'd want to wait.

As for the first 50. Maybe there are several 2103's that were sent to Europe. There aren't that many of the first 50 in the 2103 series accounted for.

Finally some questions for the list:

  • Does anyone w/ a later model Chroma have white boards for the cpu,motherboard etc.?
  • When did Arp transition to Gulbransen and did the original plant stay open as a service center?
  • How many OS versions were there? Both my machines had updated EProms w/ver.14
  • I doubt they shipped a machine that had Poly/Mono for parameter #2 but implemented it as a Footswitch parameter.
  • Did anyone on the list see the Chroma at its Namm debut?
  • Are there any existing Chroma Prototypes (Pre 21010011)?

Also an apology to Dave. I've meant to take more pictures of the CPU board but was waiting to get a better camera which was accomplished last week.

Krisnallah Sumy [21010282+] · Sun, 17 Sep 2006 18:57:55 +0200

3000 rhodes chromas

As I now understand from the billions of people living on this planet earth platform. There are approx, 3000 rhodes chromas incl. expander circulating.

Well I am glad to be a part of this family

Rob Belcher [16330123] [21030095] · Sun, 17 Sep 2006 18:01:01 +0100

Hi,

Does anyone know how many Rhodes Chroma Expanders were made?

David Clarke [21030085++] · Sun, 17 Sep 2006 14:36:10 -0400

Re: Chroma 21010022 for sale on eBay (how many Chromas)

How many OS versions were there? Both my machines had updated EProms w/ver.14

Insofar as I know, Rev 14 was the last 'official' release (with there having been a Rev 15 in the works, that I don't think was ever released).

The Chroma Computer Interface Manual lists "Rev 10" as the earliest release.

I doubt they shipped a machine that had Poly/Mono for parameter #2 but implemented it as a Footswitch parameter.

If anyone has a Rev 10 firmware for their Chroma, it would be an interesting task to see what's 'in there' (i.e., how it differs from Rev 12 - whether it has support for Poly/Mono.)

David Clarke [21030085++] · Sun, 17 Sep 2006 14:36:41 -0400

Does anyone know how many Rhodes Chroma Expanders were made?

The registry has serial numbers for Model 1633 up to 0135, and for Model 1631 up to 0010 - so if we assume no gaps in numbers (and each series got their own), then we've probably got evidence of at least 140 being made.

Dave Bradley [16330135] · Sun, 17 Sep 2006 13:42:44 -0500

Re: 3000 rhodes chromas

I have #135 of the North American ones. It was a factory left over and was one of the last ones made. I would guess that there were 150 or less made for North America, and less than that for Europe.

Chris Ryan [21030691] · Sun, 17 Sep 2006 11:54:43 -0700

Re: 3000 rhodes chromas

There are approx, 3000 rhodes chromas incl. expander circulating.

This has been a matter of debate for some time. See the threads on the topic linked from the FAQ "How many Chromas were manufactured?"

Jesper Ödemark [21010135] · Mon, 18 Sep 2006 07:11:15 +0200

Re: Chroma 21010022 for sale on eBay (how many Chromas)

So you mean that the 3 vs 1 indicate different input voltage? There were 4 used for Australia - right? Is the 2 for Japan then?

Jesper Ödemark [21010135] · Mon, 18 Sep 2006 07:29:37 +0200

Re: 3000 rhodes chromas

I think the registry is great 'cause as the years pass we will know... and as I think I've mentioned before; My experience and interest in EDP and OSC shows that all manufacturers tend to exaggerate the final numbers. It's sometimes machines sold, but often also shipped units after repairs etc.

I think the Chroma pops up for sale slightly more often than for example an OSCar. The "net" says the OSCar was sold in 2000 units. I'm still waiting for the day I'll see an OSCar up for sale with a serial above the 800's and these bastards were numbered 51 and up (with the original 50 being hand made and only some have figures inside the unit showing serial).

electronically yours, jesper - and OSCar, most probably no 35...

Jesper Ödemark [21010135] · Mon, 18 Sep 2006 07:36:12 +0200

Re: 3000 rhodes chromas

one of the last ones made. I would guess that there were 150 or less [Expanders, 1631 1633] made for North America, and less than that for Europe.

Oh! One of my Chroma's cousins in the new world! ;)

electronically yours, jesper - and #135, euro-style

Peter Forrest [21010096] · Mon, 18 Sep 2006 10:27:32 +0100

Re: 3000 rhodes chromas

I'm not the first person to point out that if Phil Dodds boasted that $3 million worth were sold in the first year, that equates to about 600. (That's assuming he was talking full market price, but that is what most manufacturers would do, I believe.) And they might have done quite well to output the same in the following year. With no number in the registry over 1000 (unless I'm missing something) it also seems statistically very unlikely that there could have been 3000.

The only way that could happen would be if the other three (non-US-market) types sold in similar numbers. Unlikely in the extreme.

What about the question of serial numbers being unique or not?

Until there was a duplication of numbers, that seemed likely; and duplication could still be a simple mistake. But the fact that the few Australian models don't have any serial number in the registry above 0016 - or the European ones above 0299 - makes me lean heavily towards the belief that the numbers are duplicated - it's just that we haven't seen many cases yet of duplicates cropping up. A mathematician should be able to work out the probability of numbers coming up twice. I seem to remember that in a class of 30 kids, it's better than evens that two have the same birthday. That's 365 possibilities, 30 examples. With 1000+ possibilities, and <100 examples, we might only expect one or two to come up

Ron's evidence about his three known examples of 23030011-60 being all ARP boards, no vents, and odd top key is persuasive - coupled with that first field note mentioning 2303 0011-60 specifically.

Of course some of the field notes might really be referring to 230x generally.... As Ron points out, the first mention of 2101-2104 isn't until the last field-note, Oct 83, which is a long, long time after 2101s were on sale in Europe.

But I'm pretty sure Ron is right. A couple of side questions:-

  1. do the other ARP type numbers (for Odysseys, etc.) also refer to geographical locations (ie most importantly power supplies)? And
  2. isn't it quite strange that an American manufacturer chose 1 as the designation for Europe and 3 for the USA?

John Leimseider [21030434++] · Mon, 18 Sep 2006 08:31:24 -0600

Re: Chroma 21010022 for sale on eBay (how many Chromas)

I repaired 2 Chromas with rev 15... Rev 15 was written by Paul Derocco to use with a controller that implemented poly pressure with key location. You could change things by moving your fingers forwards or back on each key separately... I didn't get to see the controller... The customer was planning on fixed it himself.

Ron Joseph [21030042+] · Mon, 18 Sep 2006 16:19:14 +0000

Chroma OS revisions

John,

All of my chips on 21030042 have stickers on them that tell the OS #. One says 14A.Any idea of what the "A" stands for?Were there subrevisions that you know of?

Chris Ryan [21030691] · Mon, 18 Sep 2006 09:35:30 -0700

Re: Chroma OS revisions

At least one difference between Rev 14 and Rev 14A is the velocity response, documented by David Clarke in "Chroma Keyboard Velocity Curves."

John Leimseider [21030434++] · Mon, 18 Sep 2006 10:31:36 -0600

Re: Chroma OS revisions

The A was version 14 with the velocity table fixed. When they went from 12 to 14, they really screwed up the velocity. You had to really hit the keys hard to get it soft. Version A has the rev 12 velocity table, essentially. There were a few variants around, also. I wrote one, then went to one that I think Ken wrote...

Chris Ryan [21030691] · Mon, 18 Sep 2006 09:53:14 -0700

Re: Chroma 21010022 for sale on eBay (how many Chromas)

We have only one model 2102 Chroma in the registry, #21020003, and it was originally purchased in Sweden. So the purpose of this model seems obscure.

Jesper Ödemark [21010135] · Mon, 18 Sep 2006 19:24:39 +0200

Re: Chroma 21010022 for sale on eBay (how many Chromas)

  • "Weird one, this 2102... it's made from old parts. What shall we do with it?
  • Sell it to the swedes... it's to expensive to ship back for repair anyway.
  • Good point! And the cold winters will help with the cooling issue!"

;)

Sweden was legendary for their rigorous (is that correct spelling?) electric safety controls in the 80s (now the rest of Europe is following) and forced for example Korg to change the entire MS-series when it came to PSUs. Could it be something like that? That would indicate there being at least two more sold up here...

David Clarke [21030085++] · Mon, 18 Sep 2006 20:02:19 -0400

Re: Chroma OS revisions

At least one difference between Rev 14 and Rev 14A is the velocity response, documented by David Clarke in "Chroma Keyboard Velocity Curves."

Also - there's a bit of an error introduced in Rev 14A, as noted below the 14A image on the EPROM Code page. In summary, Set Split 18 (Panel Disable) has an incorrect reference.

New feature requests for CC+

Dave Bradley [16330135] · Sun, 17 Sep 2006 14:46:42 -0500

So,

The CC+ offers a new faster CPU, more RAM, more ROM, more room for features.....

Let's start a feature request list! I'll start:

  1. Wider range on LFOs - the closer to audio the better
  2. Finer resolution on envelope parameters (0-63) - useful on the fast end if the limiting caps were removed.
  3. More filter resonance levels (might be a DAC resolution issue though - haven't looked at a schematic)
  4. New keyboard polyphony expansion modes with Expander - spill new note requests to Expander when all channels are in use.

Any others?

Jim Russo [21030433] · Sun, 17 Sep 2006 16:43:48 -0400

Random/Randomize patch generator (all parameters or selective)

Murray Macdonald [21030276+] · Sat, 23 Sep 2006 22:27:59 -0700

LFO Speeds and envelopes derived from MIDI Clock. (1/4, 1/4t, 1/8, 1/8t, 1/16, 1/16t, 3/16, etc...)

See New feature requests for CC+ in the November 2006 archives for more discussion.

21010096

Peter Forrest · Mon, 18 Sep 2006 09:52:30 +0100

Hi Chris,

Please add this one to the registry. 21010096. Nothing special about it except that it does sound great and play wonderfully, and has been fully serviced by Roy Paynter (bless him).

The only piece of trivia I can think of about it is that its top panel screws (the big lacquered ones in the wood) look original but are cross-head, while 21010022's original screws are slotted.

Disassembling a case

Dave Bradley [16330135] · Mon, 18 Sep 2006 22:31:19 -0500

Is it possible to separate all the cherry wood parts from the tolex covered parts of the case so that they can be refinished? Do I have to crack any glue joints?

Jerry Leonard [21030100++] · Tue, 19 Sep 2006 09:16:18 -0700

No you don't have to crack any glue joints. It's been awhile since I did mine, but I know that it is not glued. I believe there are brackets on the inside that hold the end pieces and the narrow strip on the top is screwed on. The front bottom is also screwed on. Have fun!

Dave Bradley [16330135] · Tue, 19 Sep 2006 12:16:03 -0500

Coolness, thanks!

Trying to resurrect Chroma

Dave Bradley [16330135] · Tue, 19 Sep 2006 20:58:18 -0500

So my Chroma has been dead for several years after moving it 6 feet across the floor. I finally looked at it yesterday and the digital 5V was dead as I expected.

I transplanted the PS from my Expander in, after checking the output voltages and flipped the switch. Boo! Either all the LEDs light, or the tapper clicks once and a subset of LEDs lights. The panel doesn't respond after that and I can't perform a Set Split 50.

What should my next step be?

(BTW, the Expander PS doesn't have the preregulator board on top of the big can).

Stu Ervin · Wed, 20 Sep 2006 13:34:10 +0000

FYI, that is not a "pre-regulator" on top of the can. Its a zener diode, basically a clamp, to prevent overvoltage on the digital supply.

David Clarke [21030085++] · Wed, 20 Sep 2006 19:25:17 -0400

I transplanted the PS from my Expander in, after checking the output voltages and flipped the switch. Boo! Either all the LEDs light, or the tapper clicks once and a subset of LEDs lights. The panel doesn't respond after that and I can't perform a Set Split 50.

What should my next step be?

Assuming the Expander was working 100%, the good news is that you have a lot of good parts to 'swap' with. (you can swap 1:1)

A good, quick first item to check is the 5V rail as seen on the CPU board.

A good debug step is to disconnect any interface which are not needed right now. The quickest/easiest of that is to actually pull out/remove all 8 dual-channel voice boards (yes, autotune should fail - but you should get to where the CPU is alive and the display is active).

A follow-on brute-force approach would then be to swap boards between the Chroma and Expander to find out what's not well.

(it could be as simple as the 'reset' line from the CPU is a bit lower/slower than it should be, and one CPU board is more senstive to it than the other).

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

Paul Tillotson [21030218] · Wed, 20 Sep 2006 18:51:22 -0700

My Chroma has been misbehaving as described here: often powers up locked up with no display and in a locked up mode. I sent it off to my now ex tech for a year's holiday and he returned it and said he could do nothing for it. In despair, I turned it on and idly touched the ring of the cassette interface port with the interface cable and it went into autotune mode and booted as successfully as it ever does, with one voiceboard out. I adjusted the trim pot for the 5 volt offset and it now boots right up most of the time, only occasionally locked up, and if I leave it turned on, it may boot in the next few minutes or an hour or so.

I know I need to get it more stable than it is now, but I'm so frustrated with what happens any time I try to get gear serviced, that I'm happy to spend some quality time with this instrument.

Dave Bradley [16330135] · Wed, 20 Sep 2006 21:05:51 -0500

David et al,

The I/O board seems to be a culprit. If I plug either connecter from the I/O board to the power supply in, the digital 5V drops from 5.02V down to 3.67V.

This happens with the CPU board unplugged from the I/O board also.

Edward Chen [21030674] · Wed, 20 Sep 2006 22:38:39 -0400

About a month ago my Chroma started showing symptoms of a faulty PSU as it would lock upon power up, leds would just flash and freeze, etc. I contacted my tech Mike Metz at Thesis Audio who has been servicing my synths for many years and he suggested I can just send him the PSU unit along with the transformer and he would have a look at it. Upon his receipt I received this initial email from him...."I found that the digital section was not working, hardly at all. The 5 volt digital supply is running just over 2 volts, and would have been causing all sorts of operation problems. I found a shorted capacitor, and a shorted regulator that is unlike any that I have ever seen. I will have do some searching for this part. This entire PSU, like most ARP products of the time is very overdesigned (in a bad way) and unlike any other circuits, but I should be able to get it repaired when I find the parts."

and here is the followup email a couple days later..."I got the parts for the PSU in today and got it up and running. However, I have a made a modification to the design. There is an old type of protection device in there that is no longer made that had shut down and damaged the PSU. The device is designed to short out when it sees over 6 volts. This shuts down the 5 volt supply if it goes "over" to protect the circuits. But, this device is installed in the PSU before the 5 volt regulators in a section where the normal voltage is 7 volts. I can't even figure out how this PSU design ever worked at all, it is so weird (thats my technical description). So, I reinstalled the protection device at the output stage of the 5 volt supply where it should work with out messing up the entire supply. There was a huge amount of talk on the forum about this kind of problem. This might offer just a bit less overvolt protection than the original design, but PSU units seldom go overvolt anyho w, they usually go under, and this device just wont ! function as originally designed. But then it was the 70's and it was ARP....I should have it ready go early next week and will let you know"

Well I got it back within a 2 week turnaround time between shipping from Kansas to New Jersey, installed it and everything worked at the first power up and has ever since then. Don't know if this is any help but thought I share my experience.

David Clarke [21030085++] · Thu, 21 Sep 2006 18:42:08 -0400

The I/O board seems to be a culprit. If I plug either connecter from the I/O board to the power supply in, the digital 5V drops from 5.02V down to 3.67V.

This happens with the CPU board unplugged from the I/O board also.

It was probably already done, but if not, all of the 'extra' cables can be disconnected from the I/O board (i.e., ribbon cable to the rear panel, ribbon cable to channel motherboard, panel flex cables, etc).

If the drop is still seen with the I/O board connected (and with everything else disconnected), then it could either be a PSU issue or an I/O board issue.

Assuming that the PSU was working fine in the Expander, the PSU wouldn't be the first thought.

When the problem is occuring, feel around for warmer-than-the-others parts. (a bit of a shot in the dark, but if an IC has failed, you may get lucky and be able to detect it this way.)

Can you comment a bit on how/when the Chroma stopped working? Was it fine one day, and not the next - or did it stop working after it was open one day, etc?

In terms of the power connectors to the I/O board, one of them carries Digital 5V/GND (J2); however, the other connector (J1) carries only analog voltages. If the 5V rail drops with just J1 installed then that might be an easier item to try to diagnose as it'd be a matter of finding where the 5V analog goes to on the I/O board. (most of the board is digital, so if it is an analog area that's affected, that'd be easier to find).

Dave Bradley [16330135] · Thu, 21 Sep 2006 22:06:40 -0500

In terms of the power connectors to the I/O board, one of them carries Digital 5V/GND (J2); however, the other connector (J1) carries only analog voltages. If the 5V rail drops with just J1 installed then that might be an easier item to try to diagnose as it'd be a matter of finding where the 5V analog goes to on the I/O board. (most of the board is digital, so if it is an analog area that's affected, that'd be easier to find).

In fact, that's the case. With everything unplugged from the I/O board that I can manage, if I plug only the leftmost connector carrying analog voltages in, the digital supply drops from 5.03 to 3.67 volts. I don't feel anything getting warm.

The original failure came when I moved the synth 6 feet across the floor. It was all buttoned up and functioning perfectly before, 2 minutes later and it was dead. Very sad!

Jeffrey D. McEachin [21030073+] · Fri, 22 Sep 2006 11:20:18 -0700

The original failure came when I moved the synth 6 feet across the floor. It was all buttoned up and functioning perfectly before, 2 minutes later and it was dead. Very sad!

It happens, unfortunately. I recently moved my wife's computer 12', and its power supply went overvoltage on powerup, taking out the motherboard and the harddrive. Seems like most electronics failures have their root cause in mechanical failures.

CC+

Riccardo Grotto [21010249++] · Wed, 20 Sep 2006 08:25:11 -0700

Hello,

I just subscribe to the list to say thank you to Sandro and David for their work.

I received 4 boards for my chromas and expanders, but haven't been able to find the right moment to install them. I did it yesterday. I completed one chroma and one expander. Installation is easy for both the units, very well explained and detailed with photos. It will probably take some time before I can go further into the new programming possibilities, but it has been a real joy to play the expander from my Korg keyboard. You can already count myself into if such projects will involve the power supply unit or a chroma knob box. thanks again

p.s. I also took note of the expander serial number whose plate was lost.......I'll upgrade the infos on the instrument registry

Jerry Leonard [21030100++] · Wed, 20 Sep 2006 09:33:18 -0700

Ditto the appreciation for David and Sandro. As a sidenote, my expander did not have a serial number either. I wonder if that may me a common thing.

Jesper Ödemark [21010135] · Wed, 20 Sep 2006 19:18:59 +0200

(Homer mode on)
*mmmm*
(Homer mode off)

Looking forward to mine (being one in batch 2). Any news on when they can be on their way?

All who add knob boxes (midi style) to their CC+ are very welcome to send info about it to the list. I looking forward to program my monster knob-style...

Chris Ryan [21030691] · Wed, 20 Sep 2006 18:30:11 -0700

As a sidenote, my expander did not have a serial number either. I wonder if that may me a common thing.

It's not even written inside? (I suppose you'd have noticed on installing the CC+.)

Jerry Leonard [21030100++] · Wed, 20 Sep 2006 18:37:25 -0700

No, I checked everywhere, even loosened the channel board and looked underneath. No serial #.

power supply

Krisnallah Sumy [21010282+] · Thu, 21 Sep 2006 01:54:37 +0200

Hi folks,

Since Rhodes Chroma PSU can not be trusted. I was wandering, when swapping the psu Can it be done with a simple ATX computer powersupply or do you have to use Meanwell T60B or Power-One MAP 80-4000 What is the diff ????????

Peter Forrest · Thu, 21 Sep 2006 09:02:38 +0100

In my limited experience, trying to use a new, modern, on-paper-much-better PSU has been very difficult.

Lucid Sound, who are excellent analogue synth techs, tried this with a very sick Chroma that had arrived, using a carefully chosen (and expensive) PSU which should seemingly have been perfect for the job. After many, many hours of work, things were still not right.

When I took it to Roy Paynter, he removed the new PSU, re-installed the old 'broken, unreliable original PSU, worked on it in his expert way, and had the machine perfect in maybe half the time Lucid had taken unsuccessfully trying to get the smart new PSU to do the right things.

FS: MAP 80-4000 power supplies

Tom Moravansky [21030431] · Mon, 25 Sep 2006 09:53:31 -0400

I have a pair of Power One MAP 80-4000 supplies for sale. One is new in the box, never used, never even taken out of the box. The second one is unused, but is missing the box (I have all the docs for it though).

$50 for the boxed one, $45 for the unboxed one.

I also have a bag of .093 Molex connectors and pins and some resistors and wire. I'll throw that in for free if someone wants both supplies. $10 additional if only buying 1 supply.

Mark A. Lange [21030459+] · Mon, 25 Sep 2006 09:05:52 -0500

Hi Tom,

I'd like your supply - drop me a private email.

Rob Vandivier [21030396] · Mon, 25 Sep 2006 11:50:22 -0400

I'll buy one and the connecters

Email me if still available.

FS: Chroma Syntech Midi interface

Jim Russo [21030433] · Mon, 25 Sep 2006 10:08:48 -0400

This unit was bought from Ken .Y a few years ago, looks and works great, as new. $70 shipped to U.S., +$5 for Canada and +$10 for Euro (They're $200 new plus ship). More info on the Syntech.

Paypal or money order ok. Email privately if interested.

Peter Forrest · Mon, 25 Sep 2006 15:12:38 +0100

Yes please!

Can I paypal you the money? I'm in England.

Jim Russo [21030433] · Mon, 25 Sep 2006 10:18:09 -0400

Peter, please email me direct. You emailed the list. THX

Jim Russo [21030433] · Mon, 25 Sep 2006 11:03:11 -0400

SOLD: Chroma Syntech Midi interface

SOLD. Thanks Peter.