Any Egnater Renegade experts out there?

[punkykatt]

Hello all, working on this amp for a friend of mine. Amp sounds great, nice crunch and overdrive and cleans, very satisfying to play. He will be playing and the amp will go dead and then come back on by its self. It will do this several times and then be fine sometimes for days. On the bench I have my bias probes and meters on the power tubes, another meter checking plate voltage on pin one of V-1.  After many many hours  having a mic in the input and in front of a radio (so I could hear what is  happening while working on other stuff), it finally cut out. The power tubes are not effected, each tube still drawing currant. The blue pilot light LED and the channel switch LED went out, and according to the schematic the 12VDC heaters for V-1to V-5 should be out also. V-1 plate voltage went to 0v. A few seconds later all came back on, went off again a few seconds and back on. What is puzzling me the most is the plate voltages on the D-1 rail for the preamp tubes.(That should not be effected) (right)? And what would be the most likely cause of the 12VDC fluctuation in the ORANGE wire secondaries circuit of the PT? Any help is much appreciated. Thank you in advance.
https://el34world.com/charts/Schematics/files/Egnater/Egnater_renegadesch_8_09.pdf

[thetragichero]

things i'd try to rule out: solder joint that heats up and briefly loses continuity. one of the heater fuses? bridge rectifier? zener diode? r1 resistor? what's the 2n3055 doing? (weird to see a 3055 not inside 30+ year old solid state gear... i don't think they even make real ones anymore, just slap the part number on other to-3 transistors)

[punkykatt]

Thank you for the reply. That 2n3055 if it is? is in a TO-220 case mounted to the side of the chassis using as a heat sink and wires attached going to the PCB. I found it some what loose being mounted with a bolt and nut. I removed  it from the chassis to inspect and found a piece of what looks like someone cut a piece of plastic to fit (I measured it .019" thick) in place of a mica insulator that should be there. Not sure if that would cause the problem or not. I orders some mica insulators, should be here next week sometime. With the V-1  pin 1 plate voltage dropping to 0v. I might have had the meter set at 200vdc instead of 1kvcd causing the meter to overload and show no volts. I did another test and with the 12vdc heaters off the plate voltage goes over 300+ vdc. These amps are not fun to work on, so many wires in a small area in the power supply PCB section. Thank you again for your reply.

[punkykatt]

Hey Guys, working on my buddy`s Renegade again. I have replaced everything but the 2n3055 transistor in the 12v circuit and still has the problem. I`m thinking of replacing that 2n3055 with a 2A 12v regulator. https://www.st.com/content/ccc/resource/technical/document/datasheet/e9/be/53/a3/1f/6f/4f/75/CD00000449.pdf/files/CD00000449.pdf/jcr:content/translations/en.CD000004 . If I connect the (input) of the L78S12C to the collector on the PCB, the (ground) to the base on the PCB and the (output) to the emitter on the PCB that should work correct??  Any comments or suggestions are much appreciated.

[punkykatt]

https://www.st.com/resource/en/datasheet/l78s.pdf