Hi - I’ve got a problem with my Korg SV1, which has been a workhorse for me for many years without any problems, but recently developed problems with the amp simulation. Sound is absolutely perfect with AMP MODEL turned off, but distorted when turned on. Reading around I thought solving this would be a simple valve replacement, but with a new valve the fault is exactly the same. I replaced the Amp Sim board that sits behind the valve but again no change in the sound. Tried adjusting the trim-pot which changes output volume but not the distorted sound. I’ve tried to get the local guy who everyone goes to with their guitar amps to take a look but he’s not willing, I don’t want to ship it if I can avoid it, so it’s a case of repairing it myself… Where should I be looking next please? The I/O board seems the obvious place, seems the caps on that board are a little susceptible at times?
Look at C81 and C64 on the main board, not on the I/O board. There are 11 surface mount electrolytic capacitors, and I’ve been seeing lots of them fail lately! C81 and C64 are the tube send/receive decoupling capacitors. Both are 10uF
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