[Arran]

Vlad;
I looks like your set has the same problem that mine did, both a bad output transformer, and a bad audio interstage. I suspect that some form of corrosion was to blame. I think that I even took the interstage transformer apart hoping that it was just a broken wire but no luck. There is a solid state substitute for these that was published in the Antique Wireless Association "Old Timer's Bulletin" but I cannot vouch for how well it works verses a proper transformer. Hammond does make a substitute interstage transformer, and Antique Electronic Supply does sell a generic one, made in Mexico.
Regards
Arran