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thanks for the manual. This is great, it has both schematic and pcb version inside. I have attached the schematic I have, it seems to be a copy of the '79 inside the manual. In the moment I have created a combined picture of the assembly and soldering side, not very professional up to now (see attachment). The background for all that stuff: The volume pot is very scratchy. One possible reason is a capacitor leakage at the previous stage which would result in a DC current through the volume pot. That definitely can create that noise. And for this work it is much faster using an existing document than doing reengineering.
BR Hans- Georg
Edit.
I have rewritten part of the mail. In the beginning I have overlooked that 2 schematics are inside the manual...
Attached Files
Last edited by es345; 10-27-2014, 12:17 PM.
Reason: pdf file didn't work, changed to jpg
For what it is worth, I have found that most Roland JC amps that have come into my shop have needed to have the potentiometers cleaned in a big way.
You probably have already done it, however if you have not, use a good cleaner/lubricant on all of the pots before looking at the surrounding circuitry or the pot itself.
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