[rsasnett]

The fade-out problem appears to be fixed! Thank you to everyone for all your suggestions, and for encouraging me to troubleshoot before blindly shotgunning in a bunch of new parts.

I just ran the set for over 2 hours, worked great. I now have full B+ at 400v on test lug L22 (in Philco manual) as expected, and no longer need to short across the horiz ringing coil.

When I was removing the Hor Out tube to get resistance and voltage readings for each pin, I noticed the VOS board at that corner was flexing a lot. On closer inspection, the grounding tie / clasp next to the HO tube had actually come loose! I checked all those clasps earlier today and verified this one in particular was connected to ground. I soldered all of them a long time ago after putting the VOS board back. But I didn't use a lot of solder, and I guess this one was either a cold solder joint, or got cracked loose when moving the TV around or changing tubes. So that ground connection was good for a cold start, but after that corner of the board got heated up, it must have moved just enough to make it fail. I added a little new solder, so now that side of the board doesn't pull up when taking out the HO tube.

My next problem is the sound output level is rather low -- the set used to have plenty of volume. But I'm going to bask in the victory glow a little before I tackle that.