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

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

-----Original Message-----
From: kennyb@... [mailto:kennyb@...]
Sent: Wednesday, May 31, 2000 10:33 PM
To: analogue@...; criostoir@...
Subject: Re: [AH] Jupiter-6 Service Question!

I would verify that the voice trigger from the CPU board is
working correctly. Make sure all of the connectors between
the 2 voice boards and the CPU board are secure. 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.

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.

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.

If you find that it is the chip then do not stop there. A
healthy Jupiter-6 does not blow voice chips without permission.
You almost certainly have a power supply that is out of spec.
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; the
decoupling capacitors, not those in the audio path unless you
want to change the sound of your Jupiter. The CPU board
all runs off 5V but you may want to check here too.

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.

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.

Kenny B.

> I just posted a note looking for a CEM3340 chip, but I want to make sure
> that would be the problem, first. If one voice of Osc-2 is dead (except
> noise), is there anything besides the CEM3340 chip for that voice that
> be bad? If so, what would be the procedure for checking it? Thanks again!
> criostoir@...