I have always been interested in these amplifiers. I have played many of them but this is the first time I got to open one up. This guy right here had really bad humming/distorted noises and it was also dropping the signal to zero. With the chassis out I started checking for bad components. There is this burnt area that the owner told me about, so I checked the components around there and I got clear readings. Removed the board from the chassis to check for bad solder joints but everything looked fine. Voltages everywhere checked out fine too. I was scratching my head for a little bit there. It wasn’t until I checked the voltages at the tube sockets that this one lug either intensified the humming/distortion or dropped the signal by just touching it. Imagine the effects of the vibrations of the cab on this bad solder joint! I put new solder and took the time to clean up both sockets while I was in there.

For a moment there I thought I had fixed the problem, but when putting the amp together and connecting the reverb pan/foot switch, the problem returned. It wasn’t dropping the signal anymore, but the hum/distortion was there alright. I disconnected the reverb pan and turned the reverb off from the footswitch and it went away again. I turned the reverb on with the pan disconnected and it came back again. Pretty obvious, right?? I got the chassis out again suspecting the op amp from the reverb feed/recovery stages was the culprit. While checking voltages, with the reverb pan connected and on, the chip finally gave up. It meant no reverb, but also no humming/distorted noises anymore!! I replaced the chip and it came back to life. Great sounding amp this is!! A tad heavy though, but there it is, one repaired Music Man amplifier.