Power transformer replacement??

[Chad Hauris]

The way I would do this is to remove the transformer from the chassis, put a 60 watt lamp in series with the primary. Connect to 110 volt ac. No secondary leads connected to anything. Bulb glows bright=short. Remove end bells, check for bad insulation. Bulb glows diim=short somewhere in the chassis wiring.
There can be carbon tracks on a tube socket or some other elusive issue causing a short. It's a waste of time to keep trying to troubleshoot it without completly removing the loads from it.

I don't get into the whole how much is it worth thing but you will often have to spend more to repair something than you could sell it for. That only matters if you're going to sell it, though.