Another Blues Jr problem

[Helmholtz]

I was on a hold to not do anything more until he decided. He did decide to do the filter caps, and I cut him a break to make it easy for him. I pulled the 47uF cap, and it is definitely bad.

Apart from bad filtering, the scope pics looks like half-wave rectification. Do you get full B+ with the new 47µ cap? Repetition rate of ripple peaks should be 120Hz. If not check the rectifier diodes/connections.

[Randall]

The 47uF was definitely the problem, it measured 6 nF out of circuit. The 22uFs measured good, but I replaced them while I was in there. Now B+ is back to normal, only a volt or two of ripple, and the scope looks normal. Amp sounds normal again. All power supply connections looked good on the board, but I hit the diodes just in case.

Glad to be done with this!