I have an Epiphone Valve Junior Combo amplifier that needs repair. It used to play fine until I decided to swap in/out a few different tubes both at pre and power section. I suspect the repeated removal/insertion of tubes and retention spring must have done something to the socket. I simply cannot turn the amp on and start playing and in less that a few minutes there is a weird crackling noise, then some hiss/static noise and then silence. I then check the tube with a tester it's dead, both the heaters (pins 4 & 5) show no continuity. I have ..."lost" two brand new tubes so far, so I am not risking putting another in there unless I identify the problem. This is a very simple design the only thing that could be the culprit is a resistor and cap and of course the voltage that is provided to the power tube. BUT, there is absolutely no problem at all with the preamp tube (which I also swapped in/out many times) so I am kinda stuck. I can follow instructions, I am good at soldering, I have a decent DMM and tube tester (albeit borrowed from a friend), I understand electronic schematics although definitely not an expert. I believe I can do the troubleshooting with someone's guidance. It is simply not worth paying a tech to look at it, it will probably cost me more than the amp's value. I am also posting the schematic, however at this early point I am primarily concerned about asking questions in a Solid State forum about a tube amp. Let me know, I hope I did not break any rules. Thank you!
EDIT (1/23): I uploaded another schematic I found online, the tube section is identical but there are some "interesting"(?!) differences in the power supply. Indeed the transformer outputs 6.3 VDC for the heaters obviously after the bridge it should be a bit higher, so indeed the first schematic is wrong (we already know that).
EDIT (1/23): I uploaded another schematic I found online, the tube section is identical but there are some "interesting"(?!) differences in the power supply. Indeed the transformer outputs 6.3 VDC for the heaters obviously after the bridge it should be a bit higher, so indeed the first schematic is wrong (we already know that).