Yeah, that's what I was afraid of. The smoke COULD be due to an internal short in the transformer, but it is more likely that the circuit started to draw excessive current, which caused overheating of the transformer and may or may not have resulted in damage to the transformer itself. The PGP 8.1 would generate a fairly high voltage, and the power supply capacitors may have gone south first, for example. Or one of the tubes may have shorted internally - they are highly stressed with the high PGP8.1 voltage, unless the circuit values have been modded.
Ping me by email (paul at bottlehead dot com) and I'll see if I can locate a scan of the manual.
You might want to test the transformer to see if it is actually damaged. To do so, measure the DC resistances of the windings - I don't remember which is which, but the solder tabs are identified by winding number and a letter code for Start, Finish, and Tap. The primary should be 5.1 ohms, and the HV secondary 315 S to F (half that S to T or F to T). This will indicate whether the transformer is actually shot or not. You can compare with the good one.
But if you really want to get at the original S.E.X. amp with TFA-204, the PT-7 is in my opinion the best way to go.
