I once had one of these. Mine had a 35W4 rectifier. After re-cap and alignment, it worked much better than the S-120 that I also had at the time. As I recall, the schematic was glued inside the cabinet which is common among Japanese-made radios. If it's not there your can see it in this post:
viewtopic.php?f=15&t=210203Because of your description, I would first suspect a shorted cap across the output transformer primary.
Dave