Help identifying transformers in a second hand build please

[olddawg]

Hi folks...I just picked up a project second hand an am hoping someone can tell me what the transfomers are and if they will be appropriate for building a 1974X Marshall TMB clone w/ an EF86 overdrive.

The PT has these numbers on a paper sticker on the bell:
PT-290 2X 6.3V
HT-6179 2X 6.3V
Someone has written 305 on two of the secondary wires.
(I was told this was an old Zenith PT, but it looks newer to me)

The OT has the numbers stamped on the bell:
99-1395
343722
(I was told this was the OT sold by Hoffman amps for 18watt Marshall clones but their site doesn't list it)

The amp is supposedly working. (though I haven't powered it up yet) It has 2X EL84s and 2 x 12AX7s with an EZ81 rectifier. The OT is also suposedly wired for an 8 ohm tap but two other wires are capped on the secondary which I am assuming are the 4 and 16 ohm taps. I'm hoping to find a color code.

[tubeswell]

Have you measured the VAC off the PT secondaries? I'd say it is rated for whatever current you have in the amp now

With the OT (disconnected) you can stick the secondaries on a variac at a low (say 12VAC) voltage and measure the VAC on the primaries (which will be much higher - so be careful). The impedance ratio will be equal to the square of the voltage ratio (of the primary to secondary voltage) e.g.;

If you got say a voltage of 344VAC:12VAC, that is 28.7:1 (344/12 = 28.7). So square that (28.7 x 28.7 = 823.69). So the impedance ratio would be 823.69:1, therefore if you stuck an 8R speaker on that you would get a reflected load of 6,589R (6k6) - 823.69 x 8 = 6,589

[olddawg]

Have you measured the VAC off the PT secondaries? I'd say it is rated for whatever current you have in the amp now

With the OT (disconnected) you can stick the secondaries on a variac at a low (say 12VAC) voltage and measure the VAC on the primaries (which will be much higher - so be careful). The impedance ratio will be equal to the square of the voltage ratio (of the primary to secondary voltage) e.g.;

If you got say a voltage of 344VAC:12VAC, that is 28.7:1 (344/12 = 28.7). So square that (28.7 x 28.7 = 823.69). So the impedance ratio would be 823.69:1, therefore if you stuck an 8R speaker on that you would get a reflected load of 6,589R (6k6) - 823.69 x 8 = 6,589

Yeah, I know the drill. I was just hoping that someone might recognize the OT as a Hoffman supplied tranny, know the color code, and might help me out.

Also, this is a home built amp. Pretty much a bunch of parts I got cheap. I was told that the power transformer was oversized and that the amp was once set up for reverb and and another pre amp tube. (There are even unused tube sockets on the chassis but this doesn't mean that it didn't have another tranny at that point or that it worked) Trust but verify. I was hoping someone could tell me what those PT numbers meant and if they indicated the max current available or could point me toward a spec sheet. Minus that, is there a way to measure a PT's max current capacity? I will be adding one more 12AX7 and an EF86. Maybe I just need to build it and see if it gets hot or the supplies are pulled down significantly. The next thing I will do is measure all of the PT secondaries with the tubes out.