[Amps] AL-80B trouble

[Roy Koeppe]

Stated;


"...SYMPTOM:  With the standby  switch in standby, band-switch set for
80M, AC power applied to Amp, the meters  read ~2700Vdc (normal is
~3000Vdc), 150ma Ip, and the Ig is showing a negative  draw.  The Ig
meter buries itself to the  left.  After 2-3 minutes in this  condition,
the plate is glowing reddish orange.   With the standby switch placed
into operate, RF applied from the  exciter, the exciter complains of
High SWR and there is no RF power being produced  by the Amp.  With the
band-switch placed  in any other position, the same symptoms apply.

      ASSUMPTION:  The  3-500ZG has a short, and or the tube is not
receiving the proper bias voltage  during off periods .  The glowing
while  in standby is due to the current draw across the plate;
dissipating ~400W. (etc.)"


Yes, this is commonplace. The tube shorts internally from grid to
filament.

73,    Roy      K6XK