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
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|