[sdiy] Jp-8 head scratcher

Maarten Halmans diy at artefacts.nl
Wed Nov 6 16:48:58 CET 2013

Hi all,

I have some serious strange thing going on in a Roland Jupiter-8 and I have 
no more clues where to look. I tuned all 16 voices and they are very nice in 
tune over all octaves. They are well tuned on start up (in test mode) and 
when the synth is on for several hours. So far so good!

The problem arrises when I use the auto tune. All voices stay tuned except 
for 2 voices(on the same voice board). Oscillator 1 of both voices is tuned 
to high. One voice is 12 cent off the other 6 cent. Oscillator 2 of both 
voices is still in tune. So I swapped the voice card to make shure it is not 
in de keyboard cv sample&holds or auto tune multiplexers and the problems 
moves with the voice card. I also disconnected all the modulation sources 
but all with no result. Swapped the CV summing amp and the transistor array, 
which does not make sense but you have to try something. I am completly in 
the dark now. Sounds familiar to someone or does someone have suggestions or 
ideas the find the problem? They are very welcome!!

Best Maarten

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