[Amps] Alpha 77Dx

[Paul Christensen]

I had an unusual condition today that seems to be the prelude of my Alpha 
77Dx's 8877 going bad.

Shortly after applying AC power (about 20 sec.), the HV was reduced from 
what is normally 2600VDC during filament warm-up down to 2300 VDC and plate 
current ran about 40 mA where it is normally biased off until the 3-minute 
timer function completes.  After the 3-minute timer completed, the amp's key 
line was working fine, but both LV and HV read much lower than normal and 
plate current was still idling around 30-40 mA where it is otherwise 
normally biased off until PTT is applied.  Observing the amp's meters, there 
was no indication of RF drive from the transceiver whatsoever.  In other 
words, there was no change between standby and either LV or HV. except that 
plate current idled at 40 mA and HV was lower in both positions.

I re-started the amp a few times.  On  each successive attempt the fault 
condition as described above lengthened, beginning at 20 seconds, then about 
60 seconds on the 2nd power-up, then 2 minutes on the third power up 
attempt, and finally everything was normal on the fourth and power-up 
attempt.  Full RF power now and everything is running 100%.  No snaps, 
crackles, or pops at any time.

Thoughts?

Paul, W9AC