On Aug 25, 2006, at 9:07 AM, Roy Koeppe wrote:
> 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,
Agreed.
> 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.
Roy K. == The hot filament helix apparently bends horizontally from
EMF during a burst of grid-current. IMO, this occurs during an
intermittent VHF parasitic oscillation. Do you have access to a
dipmeter?
>
> 73, Roy K6XK
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
R L MEASURES, AG6K. 805-386-3734
r@somis.org
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|