Well, I don't know that an electrolytic failed. I assumed it was that and changed them.

Yes, on closer inspection what I thought was a plastic power device is almost certainly an encapsulated rectifier (four wires) so if I squint a lot two should bring in AC from the transformer and the other two push mostly DC with a huge ripple factor out to somewhere (probably the electrolytics for smoothing). What am I looking for, 50/0/50 or something?

I have also found two dinky little black heatsinks with fins, about two or three inches square, with one three legged object on each. To look more closely at the three legged devices will be interesting as the legs go through the wooden case, and then are soldered to short wires so I can't just hoik the heatsinks off with the trannies, and there is a circuit board the other side with (helpfully) wires at both ends so to angle that out of the way I will have to take a lot of jack sockets off the case. And I will have to take the wires off the trannies (careful with the heat, Richard) to perform a crude check with a meter.

Must do some work now.