Egnater Tourmaster 4100 no output burned resistors but fuses all good

[Smitty02]

Tourmaster 4100 odd issues I got a Egnater TM 4100 with 4 burned resistors R178 and 179 and R183 and 184, cooked burned board also amp does not blow fuses it came in with 2 6L6's in the outer sockets and 2 EL34"s inner sockets biased at 14ma the rca connecter with the reverb driver connected is not soldered and both wires loose,, R178 and 179 are right next to 2 filter caps and the B+3 connector which is melted Relay 10 has correct 12v on the diodes, -50 on the bias connector and 478vdc on one end of R179 I ave 478vdc pins 3 and 4 of the 6L6's actually pin 4 is a volt higher. I have -45vdc on he tube sockets and set the bia up to 120ma per manual with 4 6L6gc in it...All preamp tube are testing good I have 32vdc on pin 1 and 6 of the PI tube and No output, just a crack or pop when I switch on the stand-by or pull the PI tube.... The wire from the standby to the B+3 connector is the one that is melted. all power transformers AC voltages are right here is a print, any Ideas whats going on here?? Or what may have caused all this ... I plan on replacing the burned resistors, checking the caps when I pull the power board, but as all Egaters its a pain to pull the board. I did test it with light bulb limiter and no dead shorts bulb dims after power up.... suspect output tranny bad or choke ? Odd problems here

[Mick Bailey]

Do you have the rest of the schematic showing the output stage?

32vdc on the PI - is that a typo?

Edit: just seen your schematic request, so I guess you don't have any more.

[Mick Bailey]

R 183 and 184 are effectively current limited by R182, so I'm thinking that you may have had HT appearing on your bias output at some point.

Was F5 correct when you got the amp?

Could have been a shorted power tube socket or tube, or a flashover between tracks from the adjacent filter caps. What's on the other end of R179? measure the voltage drop across it. if it's high you're looking for a short either onwards from B+4 node. First check is for shorted PSU caps and to look for signs of arcing on the board and sockets.

[Smitty02]

No it was not a typo very low voltage at the Pi and this is the only part of the schematic I could get I was lucky to get that, I thought the same thing the board at this location is very tightly packed and it looks like it arced or possibly shorted it is a strange problem. I have not pulled it apart yet I need to get the parts first but the caps dont seem to be shorted.....

[MarkusBass]

Smitty,

Did you manage to solve the problem? I've got a task to change the tubes from 6L6 to EL34 in the amp. But the more I think about the task, the more difficult it seems to me. EL34 has much higher heather current (about 70%). I'm not worried that much about the transformer, but rather that PC tracks will not be able to handle increased current. Also, the bias voltages are different for both tubes so I don't think that both types of tubes can be mixed in the amp. I know (more or less) how to make the bias voltage switch but, as you know, the amp has very complex switching matrix to limit the power (100, 50 and 20W) and I have to check whether it will work with EL34. So I'm looking for any info about using EL34 in TM4100.

Mark