[Arran]

Like any RCA from that era check over the power transformer, they don't fail all the time, but it isn't unknown either. They also used some rubber/gutta percha wire under the chassis, so that may need replacing, as well as a candohm power resistor riveted to the chassis. I also make a point not ti make offers on a set before looking at it in person, unless it's very cheap, I would look over the chassis good, and give it a good sniff, before handing over the money, unless you have an opportunity to ohm out the power transformer. The two plate pins on the rectifier tube socket are connected to either outside leg of the HV winding, a measurement between each of those, and the chassis, will tell if it's good or not, the difference should not be more then about 20 ohms between each pin and the chassis.
Regards
Arran