I was lucky enough to acquire one of these beasts about 12 years ago in trade for an NIB Grundig Satellit 700 I acquired overseas. Over the years since receipt, it has developed a very low 60-Hz hum. So, I am starting to rebuild the power-supply including all filter caps and the diodes.
Should be an interesting project. This was a kit amp, contemporary to the ST70, but more of a brute-force device at a rated 75 wpc/rms through two KT88s (6550s) per. I have NOS/NIB GE tubes that I have matched reasonably closely into pairs, so once done, it should be a very nice amp. I am also considering the potential of adding a choke - the power-supply is crying out for this - but space is severely limited both under and above the chassis. We shall see.
I welcome any thoughts or suggestions, the schematic is on HiFi engine as well as other sources. But, a picture is here: