[oldticktock]

The E.H.T. rectifier valve? it maybe low emission, I know you replaced it but was it a good one?

The symptoms sound familiar to a fault condition I read with regards to low emission E.H.T. rectifier

As soon as the brightness level of the picture is increased instead of becoming brighter the picture will increase in size and eventually disappear, I think you satisfied that criteria earlier in your posts. A test will prove that whilst a pulse potential exists at the anode of the e.h.t. rectifier little or no e.h.t. is present at the heater of cathode, I think you have also satisfied that one, have you another good spare?

Might be nothing but worth a go, I would still also verify voltages to know data and look for discrpancies

Chris

A test you can perform for the rectifier heater, is the scale lamp test. it can be temporarily to the heater supply legs to check that winding is getting what it should negligible voltage between the two leads to the lamp and any wire will do run an ordinary MES lamp holder but the whole affair must be supported to avoid touching chassis. It can be attached with removing the rectifier