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ChromaTalk Archives: September 2001

E&MM: Playing the Rhodes Chroma with the Apple II Sequencer

Chris Ryan [21030691] · Sat, 1 Sep 2001 14:41:29 -0700

I've posted an article from the April 1983 issue of the British magazine Electronics & Music Maker, "Playing the Rhodes Chroma with the Apple II Sequencer."

There's some interesting information on the sequencer software--including screen shots which I've scanned and reproduced as best I could (they were very small in the magazine).

Fwd: Rhodes Chroma For Sale (Private Auction)

Chris Ryan [21030691] · Sun, 9 Sep 2001 18:03:41 -0700

Private auction until September 30th

It had a fall and does not produce sound, but body is good and probably most parts are also. Includes Anvil case, pedals, manuals, sturdy stand, eproms, MIDI interface, MIDI and librarian software for Apple II. Pick up in Suffern, NY USA or arrange shipping. Cash, MO, bank check. Submit bid to [e-mail address removed]

Fwd: Chroma ROM set for sale

Chris Ryan [21030691] · Thu, 13 Sep 2001 21:38:20 -0700

From: "John Koumoutseas" [see Classified Ads for contact info]
Subject: Chroma ROM set

I have an extra Rev 14 rom set but I don't know how to price price it. Could you tell me what a fair price is for them?

David Clarke [21030085++] · Fri, 14 Sep 2001 20:54:31 -0400

A rough estimate for a price would be the cost of chips themselves (if bought new) + some amount (for programming, etc.).

A Rev 14 set consists of 8 2716 EPROMs.

Taking a peek at Jameco (www.jameco.com), I see you can get 2716's for $3.00ea.

Doing the math, that would work out to $24 cost for a complete set.

So - maybe $30 or so would be a fair price?

hifi Chroma?

Dave Bradley [16330135] · Thu, 13 Sep 2001 23:06:31 -0500

Well, I rearranged my studio, moved my Chroma 4 feet and now the digital +5v in the supply is deader than a doornail. Guess it's time to nuclearize it...

Anyway,

Since I had it apart with the schemos out, I started thinking about all the hiss on the output, and looking through the schemo saw lots of nasty 4558's in the signal path. Has anyone ever tried, or thought about trying, upgrading the audio path with some decent opamps like the OP275 or similar? And upgrading old caps in the audio path while we're at it?

It works for the 2600, just curious how a hifi Chroma would sound...

Luca Sasdelli [21010226] · Sat, 15 Sep 2001 17:56:36 +0200

Several years ago, I've replaced all OAs on the dual voice boards with TL072, mosfet OAs. The result is still much stable than the original one.

On my Odyssey and on a Prophet 5 I've replaced all 741/4558 in the audio path with TL071/72/74 OAs, and the background noise has been lowered in a dramatic way.

A good step has also been, on the Odyssey, the replacement of all carbon resistors with metal substrate ones, still in the audio section.

Don Tillman · Sat, 15 Sep 2001 10:32:16 -0700 (PDT)

Well, I rearranged my studio, moved my Chroma 4 feet and now the digital +5v in the supply is deader than a doornail. Guess it's time to nuclearize it...

Ouch!

Since I had it apart with the schemos out, I started thinking about all the hiss on the output, and looking through the schemo saw lots of nasty 4558's in the signal path. Has anyone ever tried, or thought about trying, upgrading the audio path with some decent opamps like the OP275 or similar?

The 4558 is considered to be a pretty reasonable audio opamp. Are you maybe thinking of the 1458, which is just a pair of cheesy 741s in a single package? I know I've been tricked out by the numbering similarity more than once.

It works for the 2600, just curious how a hifi Chroma would sound...

Now the 2600 is full of LM301's, so there's a major improvement to be had there.

Dave Bradley [16330135] · Sat, 15 Sep 2001 13:55:17 -0500

Yep, my mistake. So what is the likely culprit for the hiss on the Mono output? Is there any way to improve it?

Don Tillman · Sun, 16 Sep 2001 15:47:40 -0700 (PDT)

Yep, my mistake. So what is the likely culprit for the hiss on the Mono output? Is there any way to improve it?

I dunno. One experiment you can try is to check the effects patch outputs (channels 0 through 3). Those are two opamps upstream of the regular mono mix output (one opamp for the channel mix and one opamp for the tone controls), so that's two opamps less noise.

David Clarke [21030085++] · Mon, 17 Sep 2001 19:40:53 -0400

Yep, my mistake. So what is the likely culprit for the hiss on the Mono output? Is there any way to improve it?

Further to Don's suggestion, you can always try pulling out voice-cards to see if the amount of hiss is lessened. This will help to isolate if the problem occurs on all voice (i.e., in common electronics) or if it is just one or more voice cards.

The good news is that the circuit itself seems pretty quiet, so you're looking for a problem/failure (as opposed to a design problem).

Any telling point would be whether the noise is there all times (for instance, during auto-tune) or if it goes away some times.

Holy sticker shock, Batman!

Dave Bradley [16330135] · Mon, 17 Sep 2001 23:40:25 -0500

Ouch!

I just priced a Power One MAP80-4000 as recommended in Don's article, and Digi-Key wants $178 for one. Anybody know a cheaper route to go?

Bernie Bean [21030671] · Tue, 18 Sep 2001 09:16:05 -0700

FWL has them

http://www.flw.com/olpow3.htm

$154.00

Matt Berassimoff · Tue, 18 Sep 2001 08:18:17 -0500 (CDT)

Marlin P. Jones had them used or closeouts for $25. I sent a email about 6 months ago to the mailing list. The next catalog I got they were not listed. That doesn't mean they don't have any. I don't remember the web link or I would send it along.

Dave Bradley [16330135] · Tue, 18 Sep 2001 12:18:19 -0500

Yeah, I checked MPJA out first thing, but didn't find anything. I'll recheck.

Don Tillman · Tue, 18 Sep 2001 12:13:07 -0700 (PDT)

Hey, high quality power supplies are expenive.

You should also get the "cover" for the MAP80, an additional $11.00.

I got my power supply from Allied (http://www.alliedelec.com). It's listed in the current catalog for $156.00. I don't see the cover listed in the Allied catalog, you might have to ask for it.

For Sale -- Spare Chroma Voice Cards

Russ Lyons [21030574] · Tue, 25 Sep 2001 21:06:56 -0400

I'm selling fully functional voice cards for $100 each, I'll cover shipping cost. Only selling in 48 US states. Money orders or bank checks only. If you want references, check my Eb*y feedback.

I am also selling an entire set of keys and the switch assembly (slightly oxidized) also for $150, I'll cover shipping. I will not sell individual keys, sorry.

Serious replies only.

Thanks, Russ

David Clarke [21030085++] · Tue, 25 Sep 2001 22:04:20 -0400

Russ - I assume these probably came out of a dead Chroma. If so, would you happen to know the serial number of that Chroma?

(For the sake of the Chroma registry it would be nice to record any Chromas that we're sure are now dead/gone.)

Dave Bradley [16330135] · Tue, 25 Sep 2001 21:44:20 -0500

Is the panel membrane in good shape? If so, what would you want for it?

Chris Ryan [21030691] · Wed, 26 Sep 2001 08:04:27 -0700

(For the sake of the Chroma registry it would be nice to record any Chromas that we're sure are now dead/gone.)

I've updated the registry with several instruments I've been sent recently, including Russ's recently decommissioned one [21030574].

I did a rough check against the subscriber list and it would seem, assuming that everyone on the list owns a Chroma, that there are as many as 40 that are not represented. Obviously joining the registry is not a requirement, but I think it's a really interesting page. Please consider sending in your info if you haven't already.

Russ Lyons [21030574] · Tue, 25 Sep 2001 23:39:34 -0400

I want to clarify this, because I'm getting some other -mails. I might sell other pieces of this Chroma, but for now, I only want to deal with what I've offered up. I will list other parts as I'm ready

Serial Number tracking

Russ Lyons [21030574] · Tue, 25 Sep 2001 22:27:01 -0400

Dave has a good point about tracking Chromas which have been scrapped for parts. The serial number of the one in question is 21030574. It had serious cosmetic problems and I needed the main I/O board to replace mine which had battery acid damage.

Jerry Leonard [21030100++] · Tue, 25 Sep 2001 20:18:56 -0700

I'll take the I/O board, even if it has damage. What would the price be and how much damage?

Josue Arias [21010162] · Wed, 26 Sep 2001 10:09:30 +0200

Hi Russ,

I need a voice card for my chroma, but I live in Madrid (SPAIN), can you sell me one if I pay shipping? I can send you a wiretransfer or pay using paypal.

Here is my complete address: [removed]

David Clarke [21030085++] · Wed, 26 Sep 2001 19:40:03 -0400

I did a rough check against the subscriber list and it would seem, assuming that everyone on the list owns a Chroma, that there are as many as 40 that are not represented. Obviously joining the registry is not a requirement, but I think it's a really interesting page. Please consider sending in your info if you haven't already.

Further to Chris' note - even if you don't want to do a 'writeup' on your keyboard, it would be nice to know at least that S/N ABCDEFGH is still in existance and is/isn't working ...

Bad voice cards (how many)

David Clarke [21030085++] · Sun, 30 Sep 2001 11:40:13 -0400

Just curious, how many people out there have bad, dead or missing voice cards?

Erik Vellinga [21010286] · Sun, 30 Sep 2001 17:46:58 +0200

Dave,

One board curruntly in Error, possibly a bad contact like so many times...

Josue Arias [21010162] · Sun, 30 Sep 2001 18:19:24 +0200

1 bad voice here

Angus · Sun, 30 Sep 2001 12:45:21 -0400

I have one voice card (5) that is bad upon power up. BUT, after 1/2 hr if I turn the machine off and back on again its fine! : ) Power supply perhaps?

Mark R. David [21030170+] · Sun, 30 Sep 2001 13:43:47 -0400

At least 2, though I can't be sure if it's more until I fix the power supply :{

Jeffrey D. McEachin [21030073+] · Sun, 30 Sep 2001 10:22:11 -0700

One. But I have 2 Chromas, so it doesn't bother me.

Murray Macdonald [21030276+] · Sun, 30 Sep 2001 12:44:22 -0700

I have two chromas with a total of one bad voice card that sometimes will not pass tuning. At other times it works.

Robert Shanks [21030301] · Sun, 30 Sep 2001 18:55:53 -0400

2 bad cards

Rob Vandivier [21030396] · Sun, 30 Sep 2001 19:16:22 -0400

I do
I think
actually Bob Benchic at Synthrepairshop in Williston, FL has been trying to fix mine
for some time now
no luck
dead cards quite likely

Jimmy Moyer [21030184] · Sun, 30 Sep 2001 20:14:07 EDT

One bad one here right now. (Heat related cause, I assume. Started after I accidently left the Chroma on all day in a non air conditioned room.) On the list to debug one of these days.

Mark Hauptschein [21030668] · Sun, 30 Sep 2001 20:45:25 -0400

Count me in with one dead voice card. Just last weekend I got the dreaded "err 5". This has happened before but warming the Chroma up and a doing a few set split 50s seemed to do the trick. Not this time.

Any suggestions?

Larry C [21030864] · Sun, 30 Sep 2001 21:59:32 EDT

One bad card here. Fortunately I have a spare, but this one has a shorted Cap. It brings down the power supply and renders the Chroma useless. I found it by accident, when I was unplugging voice cards (process of elimination) when my chroma died a few years back.

Don Tillman · Sun, 30 Sep 2001 23:35:22 -0700 (PDT)

Count me in with one dead voice card. Just last weekend I got the dreaded "err 5". This has happened before but warming the Chroma up and a doing a few set split 50s seemed to do the trick. Not this time.

Any suggestions?

I figured the term "dead" in the original question meant something like "one or more components on the board are toast" and not "sometimes it doesn't pass the autotune operation, so I guess it's time to clean the contacts and go through the alignment procedure in the service manual".

Even if one or more components really are toast the board is pretty easy to fix -- I can't imagine a board with more taps into the circuit to help track down problems.

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