Can a PT go microphonic and other troubleshooting questions?

[Fresh_Start]

This is directly related to the HT short at the Standby switch described in this thread:
https://el34world.com/Forum/index.php?topic=23879.msg256874#msg256874
First off, voltages throughout the amp were amazingly close to my notes from 2009.  The only thing "off" is that one of the power tubes is only drawing about 38ma of current and the other pulled just over 50ma.  Yes, I re-biased the amp to get the hot one down to about 48ma.  (new production Svietlana "winged C" 6L6-GC tubes)

Sometimes the amp powered up fine and sounded pretty darn good.  However, I could turn it off for 10 minutes and when I turned it back on it made all kinds of weird snap, popple, crack noises even with no guitar plugged in and both volumes at 0.  The strangest thing was when the power transformer appeared to be making noises through vibration.  A light touch with a chopstick on the paper wrapping could make noise.  Turn it off, wait 10, and iit's gone again.  Voltages were fine despite apparent microphonics from the PT.  What should I do about that?  It's a Mercury Magnetics PT (customer choice, not mine) so I sure don't want to replace it unless absolutely necessary.

The other noise culprit turned out to be the phase inverter 12AT7.  There's a small, triangular sliver of silver colored glass jammed between the upper horizontal piece inside the tube and the outside glass.  A new EH 12AT7 in that spot greatly reduced the noise level.
Obviously the amp needs new power tubes, but the BIG question is should I replace the PT?
Under other circumstances I'd probably toss the porcupine into the customer's lap.  Unfortunately, any damage done here is my fault for not putting lock washers on the power and standby switches.  No, the owner shouldn't have kept using the amp after the switch came loose.  And he should've called me the moment a fuse blew instead of burning through the ones I provided with the amp and then using totally unsuitable ceramic fuses from Radio Shack.  So I guess there's a business ethics question buried in here too...
Cheers,

Chip

[shooter]

Give it to a breadboard, SS rec +cap, add a dummyload, properly spec'd Resistor n see.
if it's still there, check the bushings and bolts.  I have a Hammond that hums up amps, so it gets breadboard duty only, but it IS missing a bushing that I'm procrastinating