[sdiy] Jupiter 6 experts?

[Steve Lenham]

+1 for Doug's suggestion.

I recently repaired a JP6 which had a CEM3340 fail in exactly that way - 
its output went ultrasonic.

If you look at the JP6 schematic, there are separate +10V reference and 
-5V supply rails generated for the OSC1s and OSC2s. I would speculate 
that a failed 3340 is affecting the other OSC2s via one of those rails.

Good luck - let us know what it turns out to be!

Steve L.
Benden Sound Technology
www.bendensound.co.uk

On 15/11/2011 00:36, Doug Terrebonne wrote:
> I would try replacing the CEM3340 VCO that is stuck very high. It may
> be affecting the others. Trying swapping it with a good one
> (installing a socket would be helpful).
>
> Doug synthparts.com --- On Mon, 11/14/11, Eric
> Frampton<eric at ericframpton.com>  wrote:
>
>> From: Eric Frampton<eric at ericframpton.com> Subject: Re: [sdiy]
>> Jupiter 6 experts? To: "SDIY"<Synth-diy at dropmix.xs4all.nl> Date:
>> Monday, November 14, 2011, 3:32 PM Hi all -
>>
>> After my unusually vague, slightly panicked initial post, I've
>> narrowed the symptom down to this: the Oscillator 2's on all four
>> voices on the 4-voice board aren't working properly.
>>
>> All four of them are out of tune (one of them is out of audio range
>> - I can see it on the scope, but can't hear it), and two of the
>> three I can hear seem to have some sort of modulation even when all
>> the mod routings are turned off.
>>
>> If I change the front panel tuning while triggering those voices,
>> the oscillators move smoothly together (as opposed to jumpy, or
>> randomly) with the front panel controls.
>>
>> If I put the unit into calibration mode and do Test 7 (Linearity)
>> and go down the line (test program D-1, D-2, etc.), all four
>> Oscillator 1's respond perfectly, but all four Oscillator 2's go
>> completely flatline on my scope.
>>
>> Hitting Autotune doesn't make a difference on these oscillators -
>> it works fine for the rest of them, though.
>>
>> I tried swapping eproms between the two voice boards, no change.
>>
>> All other functions on that board seem to be working fine, and
>> everything on the 2-voice board is responding correctly.
>>
>> Thoughts?
>>
>> Thanks, Eric
>>
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