Application for a Dim Bulb Tester? Might be easier to put one together than to find a 2:1 transformer or variac.

 

Application for a Dim Bulb Tester? Might be easier to put one together than to find a 2:1 transformer or variac.

Yes, that is another option. Assuming the piano takes 120W, put a 100W lamp in series with the AC mains input.

 

A million thanks for taking the time to analyse the results of my test and to offer these suggestions. I've also been considering the possibility of testing the equipment with a step-down transformer, given that the voltage on +VCC and the -VCC appear to be more than double what is shown on the service manual. I suppose it will be a good idea to start from that point and work my way through the rest of your recommendations. Thanks

 

Oh ok. Thanks for the tip. I didn't realise that putting a 100W bulb in series with the mains AC pretty much serves the same role as a step-down transformer. I'll give it a go and let you know the outcome.

 

I was struggling with the same problem with my friend piano. You need to replace check module which is plugged near power transistors. I found two bad transistors g109 and q119 (2SA1015). Changing those transistors and remaking soldering joints solved this problem.