Help fixing power supply/rectification of old pre-1950s amp

[eddie_bowers]

I will try to keep this short. I acquired a cool little no name pre-1950s amp that was not working. The first thing I did was check what rectifier tube it had to replace it. It was a 6X5G/EZ35. I didn’t have one, so I purchased one. When I put it in, the amp worked for the most part. It would stutter with loud low frequencies played on guitar. It sounded great except for that and I played it for several days. I just happen to have the back facing me when the rectifier blew (spectacularly).  I pulled the tube and then noticed under all the dust it was actually marked next to the socket as a 5y3gt. Weird (I thought). That other tube shouldn’t have worked at all. I put a 5Y3GT in and nothing. I grabbed a solid state (diodes in a socket) adapter for the 5Y3YGT and no go. I then modified it for the pinout of the 6X5G and bingo it came to life.

I then pulled things apart and saw that it WAS wired for a 6X5G at some point. I thought maybe I would wire it back to stock, but now I’m thinking that maybe this was done because the transformer was swapped and it didn’t support the the winding for the 5v rectifier heater. I’m just speculating since the transformer is unmarked. Right now the input to the rectifier is 283V and it its outputting 294 DC with the solid state rectifier.
This is a small low wattage single ended SL6G based amp. Should I just get a new transformer? If so, what? Should the 6X5G have worked in this amp?

I don’t fully understand the outputs on the transformer, but this is what they are:
BLACK=110vac inputs
RED = 283vac/566ac output to rectifier
YELLOW with RED stripe = ground
GREEN = 7vac for filaments
YELLOW = negative side (measures 0 to ground) for filaments
YELLOW with GREEN stripe = 3.5vac but currently not connected to anything.

[sluckey]

Right now the input to the rectifier is 283V and it its outputting 294 DC with the solid state rectifier.

That should be close to 400VDC. Pull the output tube and recheck.

Filter caps need to be replaced. They may be the reason for the low B+. Could also account for killing the rectifier tube.

[terminalgs]

be warned that 6X5's have a terrible reputation in old radio circles for failure (heater to cathode shorts -> B+ shorts to ground -> PT blows). you can google it to read the stories.   It seems the 7 pin 6X4 version of the 6X5 has the same reputation.