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Fixed the problem
I thought it would be a good idea to post the results of this encounter...even if it took me nearly a month to finally get to it.
My copy of "Antique Radio Restoration Guide" (by David Johnson) says two-thirds of all tube radio problems are tube related, so I checked them first. I didn't have to go any farther.
The radio was dead, so I removed the power cord from the back and plugged it in. Using a stick I began nudging the tubes back and forth. The 7MO7 chassis uses two 12BA6 R.F amplifier tubes in parallel, and when I touched the right one the radio sprung to life. I unplugged it and after pulling the tube, I noticed a quite a bit of corrosion on the pins. I cleaned them with a small piece of Scotchbrite then doused the socket with electronics cleaner. Feeling pretty good about that, I yanked the other six and did the same thing, although I didn’t see any of the white stuff on any of the other tubes.
I played the set for over three hours today with no problems. Good volume, reception and tone. Absolutely no hum. The radios sits for three weeks and I fix the problem in five minutes? Sheesh. All that was left to do was put away the (still sealed) box of resistors and caps, my soldiering iron, the new tubes and my un-used can of freon spray. I'm a radio repairman! Well, not really, but this simple fix proves you don't (always) have to be one to solve a problem.
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