These old radios and record players with the serial filaments (50+50+12=112 volts=line voltage) would not make UL listing because of shock hazards. The reason this type of amp is so dangerous for guitar is that the strings and bridge of the guitar is attached to the chassis ground. As long as the operational knobs for the record player are plastic (not metal) it is probably pretty safe for those of us with common sense. It wouldn't hurt to install a two prong plug with the hot side of the plug NOT going to ground. Do a recap and all the standard, "its more than 30 years" old maintenance, then spin them records.