I bought a very nice antique AM/shortwave radio that looks pretty complete but just has a loud hum coming out of the speaker when powered up. It looks like the "magic eye" tube on the front which would be really cool if it ends up working. The plate on the back of the chassis says either Electrohome 3A83X-S or 8A83X-S. On the front it says Serenader. Not able to find a cross reference in a search. I'd like to find a schematic and try to fix it up for my Dad who turns 99 years old next month. Any help in identifying this radio and finding a schematic and owners manual would be greatly appreciated.