[Winky Dink]

After determining that heat wasn't the issue, I started tube checks with the 19T8 FM discriminator. Got confusing, differing short-tests on this tube and a spare 19T8, using two emissions testers but performance improved when I reinserted either the original tube or the spare. Cleaned the pins and sockets thoroughly for all tubes. Problem solved.

Thanks, everyone. Now I can get back to the AM transmitter that wouldn't work a couple of years ago.