Admiral 19A12 High Voltage Issue

[Electronic M]

Sounds like you have done most of the things I would have done.

There's a couple of things I can think of per the low HV issue. There were two different versions of this chassis one used a 5U4 and a power transformer designed to feed it's higher power filament and a version that used a 5Y3 and power transformer with a weaker rect heater winding. Have you verified the transformer part number in your set matches the tube you are using? If you happen to have a 5U4 transformer (from a chassis swap or something in the sets past) switching to a 5U4 could improve B+ If you have a 5Y3 transformer installing a 5U4 should be detrimental to B+ and will be detrimental to transformer temperature.

If the above advice isn't helpful in raising the B+ what I would do is install a pair of 1N4007s on the bottom of the 5Y3 socket in parallel with the 5Y3 diodes...You can keep the 5Y3 in for looks and the 1N4007s with their lower plate resistance will increase B+ (hopefully to spec). Increased B+ should at the very least help some with the low HV issue.