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Re: [Amps] FL-2100B input swr problem

To: "'Eric Dobrowansky'" <>, <>
Subject: Re: [Amps] FL-2100B input swr problem
From: "Jim W7RY" <>
Date: Fri, 30 Jun 2017 06:21:32 -0500
List-post: <>
Is the input and output band switch still synced? Is the bandswitch knob in sync with the front panel?

Jim  W7RY

-----Original Message----- From: Bruce Blain K1BG
Sent: Friday, June 30, 2017 5:59 AM
To: 'Eric Dobrowansky' ;
Subject: Re: [Amps] FL-2100B input swr problem

Inspect EVERYTHING between the output of your exciter and the first
components in the amplifier closely.  Test the coax to a dummy load.  Look
at the SO-239 connector on the amplifier chassis.  Use an external SWR meter
(ie, don't trust the one in your transceiver).  Eliminate EVERYTHING as a

Hope it works out.

Bruce, K1BG

-----Original Message-----
From: Amps [] On Behalf Of Eric
Sent: Friday, June 30, 2017 1:56 AM
Subject: [Amps] FL-2100B input swr problem

I am working on an FL-2100B amplifier which is exhibiting high input SWR on
all bands except 40m.

I went ahead and replaced all of the capacitors on the tuned input circuit
with new micas, including the 1000pf from the band switch to the tube
socket. I also replaced the two 200pf caps in the grid circuit of each tube.

SWR is still high on all the bands except 40m.20m will work somewhat, at
about a 3:1 SWR, but all the other bands are exhibiting a very high input,
to the point the exciter folds back hard.

I've even tried a spare set of tubes just for the heck of it. Every other
component I've checked on the input circuit is checking good at this point.

Is is possible that the 1000pf plate blocking/coupling doorknob cap could
have shifted value enough to cause such issues on the input side?That's
about the only thing left....all of the band switch contacts, both input and
output, check good.Unfortunately I don't have a 3kv cap on hand to try at
the moment.

Searching the archives I see CO8LY posted the exact same symptoms a few
years ago. But I do not see any solution to his original post.

Any suggestions greatly appreciated!



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