Roland SH-09 Troubleshoot

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Gear: dk'tronics speech synthesizer :P
Location: Greece

Roland SH-09 Troubleshoot

Post by Yekuku » Thu Sep 17, 2020 12:48 pm

Hi VSErs :)
I have a problem with a SH-09, when amp release is used , during the release stage the pitch drops.
The synth works ok for 1 minute when it is cold, but after that period the problem appears.
Also , when the synth is controlled by external CV, it is working ok.
All these symptoms made me think that it would be an easy repair, common sense says that the capacitor in the sample and hold keyboard CV circuit should be the culprit, because when a key is released it does not hold the charge so the pitch drops during the release but unfortunately i dont see a capacitor used for this task. Could it be that C2 is the S&H capacitor ? I am expecting this cap to be before the portamento circuit.
I am afraid that IC2 could be the problem, but I thought would ask here first for ideas before hunting for exotic (rare) components.
Any ideas on what other things to check?
It is all about sharing...

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