Hello everybody, this is my first post here
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I have problem with my Yamaha PSR-12 keyboard. The AUX out doesn’t work, when I try to connect it to LINE-IN on my PC terrible loud noise continually comes out of the speaker on the keyboard and I get nothing on the PC. The connector also seems to be very sensitive. When I just put my hand near it speakers make noise, not so loud as when it’s connected but they do. Also there is always quieter noise on speaker and headphones output, but I think it comes from the amplifier and it’s normal.
The keyboard was damaged from battery leak. I already removed all the rust and replaced destroyed diode on the keys PCB and one resistor near the main CPU. The output part didn’t seem to have any corrosion on it.
I don’t know anything about analog/audio circuitry, so I don’t know where to start. I have good multi-meter and crappy kit oscilloscope DSO138. My soldering skills are good enough for the trough-hole parts in this keyboard.
Service manual with schematics and board layout is available here:
https://elektrotanya.com/yamaha_psr11.rar/download.htmlIt’s for different model but the hardware is identical.
Please help me troubleshoot and fix this problem.