AUDIOPAX MODEL 5S transformer overheating

[Subchannel]

I have an old Audiopax Model 5S preamp (from 2003 I think) with separate PSU that looks really home made.
When powered on, the transformer turns really hot, so hot that it smells like burnt electronics, and way too hot to touch.
When connecting the preamp through amp and speakers, there´s only sound in Left channel, and there´s some low frequency noise there (woofer moves back/ forth slowly, 4-6Hz).
The PSU behaves the same with and without the preamp connected.
When opened, there´s burn marks around a spot on transformer, and what looks like overheating around a few wires.
There´s one lose wire, that logically should be connected to the vacant spot on the transformer primary, but when connected the fuse in my house blows.
I´ve sent three emails to the manufacturer, but no answer (not surprised).
There´s no schematics or data online as far as I can see.
Anyone here with experience around this problem?
Thank´s in advance.

 

[RVT1K]

Is there any kind of identifying marking on the transformer that could be used to find a data sheet for it?

 

[gadget73]

Maybe unhook the transformer from the boards and see if it still runs hot. That would be a clue if the transformer itself is the issue or something downstream

 

[Subchannel]

Thank you very much for replying.
No markings what so ever.
I actually got a very detailed respons from Audiopax this weekend. Not all info are available as the current manager has only been there from 2010, but he wrote a very detailed explenation of the PSU, and that this was indeed an early prototype.
I will remove all wires from pcb´s and measure the transformer alone, which is 160-0-160V ans 12-0-12V primary. this will at least tell me if the transformer is ok.
The schematics sent is for a M7, so a more recent model, but he confirmed that they are almost identical.