This little keyboard amp came to me with a fault of not making a useful sound.
Using the effects loop trick I was able to work out that the pre amp was at fault but the power-amp was fine. Since this amp has three input channels it is inlikely that all three pre-amps are going to be duff – another clue. There is a comining op-amp that mixes the three input channels into a single feed into the power amp – surely that has to be the issue. So replaced the TL072 op-amp fixed the issue immediately, cleaned the flux off the PCB and the amp is ready to go.
It’s actually a great little amp. Three channels. Inputs for CD /IPOD using phono sockets, effects loop and a lovely reverb. I used it for a www.lovevultures.co.uk gig playing bass and it was delicious, the big speaker could easily have handled our keyboard player too.