Tony we are in the same way
I think the problem is sitting in the high voltage area of the scope.
But the measuring of that requires correct voltages from the PSU, that thing is connected allover (not shure in moment, -150, +100, +225 and the cold primary end of the HV transformer at +350 or +500V)
He have to test the kathode of CRT, high negative voltage, if that is wrong, he have to check the isolation resistance of the filament wire from CRT related to ground, chassis.
The most possible problems here are a bad isolation in the filament wire of the transformer, or that must be recapped with a small pack of 10nF/3kV ceramic disks.
A tired double triode (regulating of HV, mostly E82CC) is also possible.
I have no 545 in my collection, but the 545A, they are strong relatives.
531A, 533A and a couple of 535A is also at home here.
They are all restorated.
greetings
Martin