[Amps] Alpha-76pa Question

[Tom McDermott]

A couple of items:

	1. Older versions of the 76-PA took 100 watts drive (was part of the
FCC rules at the time). Later versions have the low-drive modification to
reduce the drive requirement to about 50 watts. Some older serial numbers
were retrofitted with the low-drive modification.

	2. The tank coil in some amps had a tendency to short two adjacent
turns, which slightly weld together due to the high current. I had to snap
apart two turns on mine, that improved performance a lot.

	3. The zener sets the idling bias of the tubes. If the no-drive bias
is correct, the zener is likely fine. Mine shows 120 mA idling current with
the SSB button engaged (plate voltage 2.4 kV) and no drive.

	4. If the plate voltage is low (CW switch engaged, plate volate 1.6
kV), the amp puts out about 2/3 of the  power.

	5. Are you running the amp from 230V? Have a 50-ohm load?

	-- Tom, N5EG





> Plate-current-platevoltage-grid current normal...amp only puts out 400 w.
Put 
> in new set of finals...same result. I am leaning towards a 5.1v/1 watt
zener 
> that is in the cathode bias line...Am I looking in the right direction?
>
>
> 73, Carol