[Amps] AL-80B unusual plate current behavior

[Rick and Theresa Low]

Several times in the past week I’ve observed unusual behavior from this single 3-500Z amplifier and need to know if this looks like the tube is about to go belly up on me, or if there is some circuit factor that’s causing this behavior: 

1. First turn on, plate current indicates about 200-250 mA without amplifier going into transmit mode. I turn ON with the standby switch in STBY. Stays this way for about 3 to 5 seconds, then zero current.

2. At seemingly random times during T/R operation, plate current meter shows same 200-250 mA, input circuit shows HI SWR on the driver rig, and of course, no RF output. Cannot clear by cycling T/R relay---PTT. I turn off, wait about 10 seconds minimum, then turn on and get the same “First turn on” behavior above.

De Rick I0/N6CY Gaeta IT JN61sf