[codefox1]

Agree with all, Key thing is time before symptoms occur. A diseased mica typically starts misbehaving from 0-60 seconds from a cold start. Note well (N/B) the comment about values, I've seen anywhere from 10 to 220 mmf in cans. Also could be any silver mica outside of the cans in the front end. If the covers to the cans come off easy, replacement shouldn't be too hard. In this instance it is OK to cut out the old part at the component body, loop the old lead and use a heat sink (transistor or roach clip, you probably have one or the other) in order not to disturb the coil connection joint. Then cut the leads of the replacement short and make another loop, join, crimp, and solder quickly and carefully. Then do the same on the other side. Well that's how I do it.

Could also be a resistor that is going bad if the set plays for, say 5 or 10 minutes before crapping out. For a nickel apiece I would replace 'em all, except for wirewounds and candohms, and I usually do this as I am recapping. The old resistors almost always drift high, and will continue to climb, so the set may only work for another year or two.