I succeeded to repair my old Traynor 25B bass amp (which I asked and received help for in this group a few months ago), however I now have another problem with it.
Background: amp was producing a loud hum, originating in power stage. I was recommended to replace some of the transistors, so I changed them all. Problem solved. Here's the schematic btw:
Now at least it sounds as it should, but it quickly becomes devilishly hot. It features two power transistors (BD911/912, formerly TIP100/105) screwed on to an aluminium plate which is screwed on to the steel chassis (applied thermal paste as well). I attached insulating silicone washers to the transistors, and use nylon bushes to electrically isolate the screws and nuts from both the chassis and the transistors, and the ohm meter assures me that the plates of the transistors are not in contact with the chassis (which is grounded) and thus not leaking.
After only 1=BD minutes of operation, the chassis around the BD's are hot enough to burn yourself on. Ten minutes later, the whole back and bottom of the steel chassis is scorching hot, as well as the transformer core! Something is clearly consuming a lot of power, but the fuses do not blow. There is one 800mA slow blow fuse before the transformer, and two 1.6A slow blow fuses after, in parallel. Just as it's always been, as well as according to the schematic.
Voltage levels are fine, at least before and after the rectifier diodes. The amp did not get near as hot as this when it was in working condition last time. What do I do?