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Subject: FW: [AH] Jupiter-6 Service Question!

From: "Verschut, Ricardo" <ricardo.verschut@...>
Date: 2000-06-02

-----Original Message-----
From: Kevin Lightner [mailto:heaven@...]
Sent: Wednesday, May 31, 2000 11:26 PM
To: Analogue Heaven
Subject: Re: [AH] Jupiter-6 Service Question!

This is just MY 2 cents worth.
I'm not trying to be a jerk here.
Don't take anything personal....

> Also, the
>sockets on the Jupiter-6 can sometimes allow chips to walk
>out. Gently (and anti-statically) push down on all the socketed
>devices to make sure they are seated correctly. If you have
>steady hands and a clean repair area you may also try pulling
>the chips and scraping off any oxidization with a scribe and
>putting them back.

I've don't recall seeing sockets for the CEM's in a JP6.
If I'm wrong forgive me.

>Get the service manual and follow the complete calibration
>procedure to the letter. The Jupiter-6's design and layout
>is fairly elegant so it is not difficult to do this.

Calibration won't bring back a dead CEM.
Just as you wrote below that there must be a reason for a CEM to
blow, there must also be a reason to have the calibrations vary.
Quite often, people don't know how to calibrate a synth well or don't
have the proper test equipment, so advising someone to do it may
result in a synth that is more out of whack than it was before.

>To see if it really is your CEM chip, try swapping it with
>another voice's. If the bad voice moves then you know it
>is the chip.

Good advice, though again I don't recall any sockets in JP6's.

>If you find that it is the chip then do not stop there. A
>healthy Jupiter-6 does not blow voice chips without permission.

CEM's blow just for the hell of it all the time.
Especially 3360's and 3310's.
Afterall, why didn't all the others also blow? ;-)

>You almost certainly have a power supply that is out of spec.

Boo!.. wrong. Bad advice.

>Check very closely with a scope the + and - power rails
>on the voice boards. There should be no noise and no AC coupling.


>Old capacitors on the voice board could need replacing

Tantalums -do- often fail, but their failure mode is often one where
they short.

>If there is any hint of a bad power supply then get a new one
>in right away. You will find power supplies are a lot cheaper
>than CEM chips and a lot of problems seem to vanish with a
>clean power supply.

Price a new JP6 power supply from Roland and I bet it'll cost a lot
more than a CEM chip from Paul or me. Putting in another supply isn't
always easy and you have to match voltage, current, temp, size, etc.
Not a simple jb to do right.

>Finally, do not replace your power supply with one of those
>cute little switchers. Their cuteness hides a fatal flaw;
>they are so noisy!!!!! Use only a linear power supply.

Some do, but switchers have come a LONG way.
The Andromeda uses a switcher for example.

Again, not trying to step on Ken's toes, but chances are great that
the CEM3340 itself died on that voice and little else is a problem.
Of course, support circuitry should first be checked.