Problems with Zenith K731

[DaveWM]

low voltage will cause the osc to stop, killing all sound (no rushing sound between stations) the pop could be the sudden start up of the osc. Fix the diode then check the B+. Reversed diode could damage new B+ filter caps.

I generally monitor the B+ and then do a slow variac startup whenever I replace diodes. You can quickly see if the B+ is the correct polarity at the very low voltage to make sure you have no wiring errors in how the diode is hooked up (as in reversed you will see neg voltage at the positive term of the filter cap, but if you see it when its low volt no damage will be done).