[rfeenstra]

Russ.  I think you are right about the leakage.  As I recall, when I tested the tubes that I got from Bob,  several showed leakage on my tester even though they were supposed to be NOS tubes.  Probably the point is they are new OLD stock tubes!

[Phlogiston]

It is likely that one of those is causing the pop on warm-up. You might try shuffling them. On my Panatrope a strong 1st audio is always noisy - or hum. So I just use a good one ~900 gm, no problem