With no power: disconnect all secondaries and measure the 345-0 and the 0-345 taps in Ohms.
Both sides should be the same; if you got around 20 Ohm difference the PT is gone.
They should measure around 40-50 Ohms per side. When measuring both 345 taps it should be around 90-100 Ohm.
There is a heavy paper? cover with the various voltages marked on it covering the bottom of the transformer. Is there any easy way to remove this without damaging it or do I just cut through it and peel it back. The soldered terminals seem to be well under the cover. I dont want to destroy or damage it if there is an easy way to remove it. Thanks AJ
Just unsolder the secondaries that go to ground and rectifier board, also the bias tap and filaments. 'Don't mess with the PT paper covers, just look where the wires go and unsolder them. You could use one of Nik's splendid layout for orientation.
If this too difficult: consult a local tech.