[Jayce]

One way my late friend used to test power transformers was to pull the rectifier tube and turn the radio on. If the tubes light, that is a a good start. Then, he would watch for any smoke and odd smells and if the set could be on 15 minutes or more without the transformer getting super hot, there is a good chance it is ok. I've used that method myself and it seems to work for an initial check. One other way to check is to pull the chassis and look for melted tar. If you see a good bit of that, beware!