Heyyo, first post on this site!
Recently I picked up a 1974 Silverface Concert Lead. I got it with issue- bad transistors, old electrolytic caps, carbon comp resistors, and a burnt R306.
I replaced the resistors with metal film resistors, recapped with a mix of new electro caps except for the big 3450uf filter caps- I replaced those with 6800uf filter caps from a later red knob concert lead. This worked for a couple of days, but after having it cranked for a few minutes, R306 totally burnt out again.
I'm trying to figure out what the issue could be. The driver transformer doesn't seem to have any shorts, filter caps look good. My thoughts are possibly the bridge rectifier off of C1, but I'm not certain as this is my first time troubleshooting a solid state amp.
