[Hallicrafters] HT-44 comments requested

[Waldo Magnuson]

I have a couple of questions regarding the HT-44 transmitter.  My HT-44 
peaks nicely with the driver and final tuning. The output appears 
adequate, but all of sudden at unpredictable times the output goes to 
zero and I have to tweak the driver tuning to get output again.
1) For HA-44 owner/operators: Have you observed any such behavior?
2) For experienced (old hands) transmitter people: What could be the 
problem?  What would you recommend I start checking (some resistors 
have already been replaced and all of the tubes checked and power 
supply capacitors replaced).  I have not aligned the transmitter.
Thanks.
73, Skip W7WGM