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ChromaTalk Archives: April 2003

Weak Powersupply - Replacement in Europe?

Michael Zacherl [21030253]

Hi Don,

Don Tillman wrote:

It would probably be best to go through the calibration procedure in the manual.

I started to go through the PS adjustment procedure. I hooked up my scope and measured the ripple auf the 5V voltage at the connectors of C3. (I checked the screws and connectors if they are clean, fastened etc. - everything seemed to be ok). The cursor showed a minimum dip of 5,62V and the max. peak was 6,62V. The frequency is a perfect 100Hz. The manual talks about a max. ripple of 0,5V p-p.

Then I carefully examined the range of R46, watching the peak ripple not to exceed 7,00V. Turning R46 fully CCW the max. peak value I can achieve is 6,82V. The minimum value is 5,4V.

The manual says, that the minimum dip should be about 6,2V - I can't achieve more than 5.94V.

Doing all this measures I switched the unit on and off several times. One single, lone moment the Chroma came to life - blinking all leds 5 times and showing a "1." as a program number. This did not happen a second time until now.

And now for the "funny" part - the last time I switched on the unit to check voltages at C7 and C11 the fuse blew up (as soon as I touched the switch).

Now the unit plays dead .-(

As far as I can see the fuse is soldered in (I can't believe this).

Well, it looks like I'll have to dig out the PS board - and as far as I can see that's gonna be quite funny ...

A nice feature of switching supplies like the PowerOne unit is that they work over a really wide range of input voltages, including all worldwide line voltage standards. So they adapt automatically. The PowerOne web site lists distributors all over the world.

Meanwhile I found a distributor here in Vienna. I didn't call them but I know the company - I'm pretty sure they will have this part.

Thanks for your help!

Michael Zacherl [21030253]

Hi Sandro,

a quick look at connectors, boards and other guts showed the unit in pretty good condition. This is not what I expected seeing all the rotten foam sticking on the exterior casing.


Michael Zacherl [21030253]

Hi David!

David Clarke wrote:

If the keyboard has been stored for the past 3 years, it would be worth taking a quick look at the CPU board and make sure that the two AA batteries haven't leaked. If they have, then some cleanup/repair will be required.

I checked them too, they may be old but everything's pretty clean. Also the connectors are in good condition. I checked them with a magnifying glass whenever possible.

Here's hoping you have some good luck in bringing the keyboard back to life.

Me too, me too.

If you run into any problems and have questions, just let us know.

Could you read my recent post (respond to Don) regarding the fuse? At the momnet I feel pretty p..... - It looked good for a short moment, but then. I've no expalanation, why the fuse blew off :-(

Thanks a lot,

Michael Zacherl [21030253]



besides that - any chance to change the fuse without taking apart the entire Chroma?

Sandro Traversi [21010217]

Re: Fuse


My Chroma has an attitude to "eat" fuses and fuses (500ma) , but I got only rapid fuse whereas Service manual advices slow blow fuse...hard to find in Italy. Now (since 2y) I got a 1000ma fuse without such problems ...

Michael Zacherl [21030253]

Re: Fuse

Hi Sandro,

I'm not sure if I made my point clear: The fuse is soldered in and since it's located in the small gap between the case and the transformer I don't see a chance to change it without taking apart the whole thing. But I'm still hoping to miss something and finally to be able to replace the fuse without that hazzle.

David Clarke [21030085++]

Re: Fuse

besides that - any chance to change the fuse without taking apart the entire Chroma?

If it is a soldered-in fuse, and if you can't get easy access to be able to solder to the top of it (due to nearby obstructions) then unfortunately some disassembly will be required.

The easiest thing to do would be to simply remove the power supply itself right from the body of the Chroma.

If the power supply itself has a problem - then you probably were going to have to remove it anyway (for any repairs it might need).

On that topic - while the power supply design is not the best - it is also not too bad (I have multiple Chroma/Chroma Expanders still all running with their original power supplies). Rather than replacing the power supply, it may be cheaper/easier to repair the existing one. The service manual should provide enough information for any electronics tech. to be able to do the necessary work.

Good luck.

David Clarke [21030085++]

Could you read my recent post (respond to Don) regarding the fuse? At the momnet I feel pretty p..... - It looked good for a short moment, but then. I've no expalanation, why the fuse blew off :-(


It is possible that turning the Chroma off and on provided enough stress on the fuse to blow it - but it is also possible that the rating of the fused needed to be changed.

There was a technical bulletin on this behaviour that recommended a change in the fuse value. A copy of the bulletin is available on the Chroma [see Primary Fuse].

Also - depending on the serial number/model of your Chroma, there might also be one or more Field Change notices that are applicable.

(If you haven't done so yet - it would be nice to have an entry for your Chroma in the Chroma registry.)

Chroma Patches

David Gowin [21030611]

Good morning and I hope all is well with you!

It seems the community that you've started here is full of really amazing and helpful people who are happy to share their stories, problems and tips for other Chroma users.

Was wondering what you might think about a small "project of everyone sending in (via a mutually agreed format) their favourite Chroma Patch(es) and making a compilation?

Thanks and have a great day!

David Clarke [21030085++]

I could probably dig out a few of my fav/most commonly used patches that I could contribute.

Anybody else have any favorites that they'd be willing to share?

Chris Ryan [21030691]

I think this is a good idea. When I started the site four years ago, my assumption was that it would be an obscure backwater where a few owners might pick up some patches. I was pretty far off on that one!

A few thoughts:

I wonder if there should be some limit to the number of patches each person would contribute. I'm assuming no one has the time to sort through hundreds or patches, either in terms of picking the best or auditioning them for use. I still have not heard every last one of the patches in the forty-two "Chroma Cult" banks [see Patch Downloads]. Maybe others feel differently; maybe a dump of hundreds of patches is a good thing, too. Or maybe only a couple of people will contribute. (There are about 75 subscribers.)

Also, and related, I always thought it would be a good idea to have some short audio samples of patches. An interesting project would be to come up with a little riff that could be applied to any timbre and give a sense of what it's like.

I have so rarely received patches for the site, I wonder how many owners either have original patches or are willing to share them. But I think a compilation is a good idea, so I will gladly compile anything that I'm sent.

David Clarke [21030085++]

Chris Ryan wrote:

I wonder if there should be some limit to the number of patches each person would contribute. ...

How about people contribute the 5-10 patches that they find most 'useful' or ones that they especially like. These could then all be combined into one bank (or two, depending on how many people contributed, etc.) When submitted, contributors could indicate why they chose the patches that they did.

Chris Ryan [21030691]

Sounds good. I think it would make sense if they were submitted in Chroma Cult sysex format.

David Clarke [21030085++]

Some Patches to Share

There hasn't been a flurry of patches being posted, so here are some to start things off.

Each file is a single patch in Chroma Cult Sysex format (126 bytes). Each is destinated for patch location 50 (so if you load the patch - to audition it - it will end up in patch location 50. You can then copy it to whatever location you want before loading in the next patch).

These three always seem to say in my Chroma (and find there way into tracks where I'm not satisfied by what is coming out of the drum machine.)

File Description
S_HH.SYX A percussive high hat, short decay
M_HH.SYX A percussive high hat, medium decay
L_HH.SYX A percussive high hat, long decay
STRANGEA.SYX A spacey pad. Sort of a space-pad type patch. For some reason this patch reminds of the Canadian band Strange Advance.

See Patch Downloads for samples of these patches.

David Clarke [21030085++]

... it looks like the .syx patches didn't come through very well as separate attachments - so here are the 4 of them again in a single .zip.

Mark David

Chris Ryan [21030691]

Does anyone know what happened to Mark David? His "Windows Interface for the Chroma" pages have disappeared, and his e-mail address is no longer valid.

David Gowin [21030611]

Could be he just changed internet/hosting providers and will pop back shortly?


Forgot to mention this when Chris first asked about Mark David's pages but there is a really great resource available at:

If you know the URL that is no longer available you can enter it in at the site and look up past versions of a web page back to 1996. I use it quite often and it works a treat. They have some insane amount(100 terabytes or so) of archived web pages online!

Mark R. David [21030170+]

Arggh!!! I've de-materialized!!!

As a result of the transition from to (and soon to, I am currently [e-mail address removed]. My Chroma interface is still operational, though I never put it back up after the transfer. I will, if that's what people are looking for.

I haven't done much with it for a couple of years or so, as during that time I've either been working furiously or not at all ...

See A Windows Interface for the Rhodes Chroma.