[MrFixr55]

Hi Fernbach, 

If you left the PM speaker and resistor in the circuit and cycled the power many times without having a pop, and if disconnecting and connecting the antenna while using the PM speaker did not yield a pop, it still sounds like the issue may be in the field coil or in that part of the circuit. When you subbed the PM speaker, did you sub the transformer also.  I have had them arc.  Arcing in the output transformer is usually visible, but if the issue is further inside the transformer, the arc is not always visible until it actually starts to burn out.  

I only have a few radios with a field coil and will have to fire one or 2 up to duplicate the issue.

Although I would think that the arcing may be visible, if the issue is further inside the field coil, it may not be visible.  However, you may hear the click (if your hearing is better than mine) from the arc.

I hear you about not going crazy if the issue does not occur while playing.  It will either work or smoke.   Unless the arcing is from field coil or transformer primery to ground, the issue may not be harmful.  However, if the output transformer primary opens, the output tube may fail from an overheated and melted screen grid.

Good Luck.