Yamaha Silent Guitar Fix
I've owned my Yamaha Silent Guitar for over 15 years and at some point I plugged the wrong power supply into it and what seem like forever it has work sporadically, if at all.
So I looked at the circuit board and noticed two capacitors looked slightly rounded tips, so I unsoldered them and I tried using my cheap multimeter to test them but I get any meaningful readings so I bought a DEOK Multifunction Tester
At this stage in my understanding of things electronics I can estimate from the displayed information that both capacitors were not performing as best they could so I bought two replacements and soldered them onto the board. I found that the guitar won't power now from the mains adapter where before it did but with terrible noisy audio and the reverb effect didn't work at all. But now at least I can plug in a 9 volt battery and everything works perfectly. I'm delighted with my first attempt at fixing old kit. The only other way of sorting out the problem would have to been to buy a completely new or second hand silent guitar.
I think I will try an experiment at the weekend where I plug the guitar into the mains and see if I can take readings with my oscilloscope and learn how to use that to trace problems. An important place to start would be finding out where the ground lead should be connected from the oscilloscope lead.