[NostalgiaRadioTime]

Thanks for all of the great ideas. I found something tonight that may add a piece to the puzzle.

I did a filament voltage check on all of the tubes. Pins 1 & 8 on the loctals, and 2 and 7 on the rectifier. I checked them cold, after 2 minutes and after 5 minutes. This was done WITHOUT the dial lamp bulb in the socket.

14B6 13.3v (cold), 12.6v (after 2 min), 12.3v (after 5 min)

50A5 46.5v (cold), 46.5v (after 2 min), 45.8v (after 5 min)

14A7 11.7v (cold), 11.7v (after 2 min), 11.7v (after 5 min)

7A8 7.5v (cold), 7.3v (after 2 min), 7.3v (after 5 min)

35Z5 44.4v (cold), 44.0v (after 2 min), 45.6v (after 5 min)

As you can see, they stayed fairly stable. However this may be a clue:

I left the leads from the meter on pins 2 and 7 of the 35Z5, turned the set off, and replaced the dial bulb into the socket. When I turned the set back on, I got 35.8v, which quickly jumped to 36.2. After only 1 minute playing, the volume dropped dramatically, and the dial lamp bulb started glowing brighter.

With the bulb out of the socket, the radio was playing fine. Volume stayed steady. But obviously not a good thing because the 35Z5 was running nearly 10 volts higher than it should without the bulb to bring the voltage down to around 35v.