[Boatanchors] general PA question

[W2HX]

Give that man a cigar! Yes, this is a harris RF-110A.  I have the manual,
apc and ppc cannot be set according to the procedure. Basically the steps to
set these do not give the prescribed results.  This is what started me down
the road to figuring out what is wrong with this amp. This along with the
other problems:

The unit runs in AB1 for voice and class B for CW and RTTY/RATT. So why are
the finals designed for 0ma in idle? 

a) 100ma plate current when idle (manual says 0ma even in AB1). According to
the manual the unit is keyed on and off through the bias levels applied to
the 4 tubes. The keying circuit switches the bias voltage for the driver and
final amplifier tubes from cut-off to operate.  Is it possible that 0ma for
plate current is consistent with cutoff?

b) plate current exceeding specification. >800ma when spec says no more than
750ma. Could I have parasitic oscillations?  

c) overload condition on 80 meters (using a dummy load). Overload circuit
trips for a bad condition on either the plate voltage, cathode current or
SWR. This is not SWR related (I checked that) but could be excessive
instantaneous plate current that can't be see on the meter (shuts down very
quickly)

I will send a note to the harris lists about this as well. But it seems most
folks agree that there should be some plate current when not keyed in a
normal operation of a 4cx1500B. Seems harris had other ideas.

Other operating parameters.
Amp keyed, no rf input, the plate current should be 240ma-280ma.

Ok, it sounds like either
a) bias is off 
b) tubes are causing grid current to flow which is affecting bias

I'll keep digging. Thanks everyone
Eugene W2HX

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of James M. Walker
Sent: Saturday, April 11, 2009 2:47 PM
To: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] general PA question

Sounds like you are running a Harris RF-110 PA.
If so you will need the manual for the Amp to check the
APC and PPC control settings.
Jim
WB2FCN
"Yep I got one of those"

----- Original Message -----
From: "john" <johnmb at nc.rr.com>
To: <boatanchors at mailman.qth.net>
Sent: Saturday, April 11, 2009 12:26 PM
Subject: [Boatanchors] general PA question


> >The unit runs 2 4cx1500B's in parallel driven by 2 8122's in parallel.
> >YWhen keyed at 1KW output, I get a little 750-800ma plate current.
>
>
>
> You ought to be able to get about that just out of the 8122's themselves.
>
> John K5MO
>
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