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

To: Bruce Blain K1BG <>
Subject: Re: [Amps] FL-2100B input swr problem
From: K2CB <>
Date: Fri, 30 Jun 2017 07:57:43 -0400
List-post: <>
When the amplifier is in standby, the SWR at the exciter in bypass mode is 
fine. So the only thing that leaves is the piece of coax between the relay and 
the input portion of the band switch. I plan to try a temporary replacement 
later this morning.


> On Jun 30, 2017, at 6:59 AM, Bruce Blain K1BG <> wrote:
> 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
> possibility.
> Hope it works out.
> Bruce, K1BG
> -----Original Message-----
> From: Amps [] On Behalf Of Eric
> Dobrowansky
> Sent: Friday, June 30, 2017 1:56 AM
> To:
> 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!
> Thanks.
> Eric
> K2CB
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