I would be trying some new tubes.
I use a TS 520 driving a 30L-1 linear, which isnt much different than what your
friend is doing, othe than the 30L-1 uses
four 811 tubes instead of 2 of the 572b tubes. Other than that, the two amps
are about the same design.
You should not need an antenna tuner between a tube output rig (the 520 in this
case) and the input of the older amps. The tube output transmitters have a
pi-network output, which is, essentially, the same thing as an antenna tuner.
I also have an FL2100B amp, which was not putting out its rated power and the
tuning controls were all off, as you say yours is. When I replaced the tubes
with known good ones, all the problems cleared up. I am now getting 650 watts
out of the FL2100b, driving it with my TS 520 at 80 watts output. The 520 is
rated for 100 watts out, but I know my original finals in my 520 are getting
along in age and could use replacing. However, I have not replaced them
because I am still able to work what I hear bearfoot, and if I need the little
extra "umph" I turn on the 30L-1. My fl2100b has not been placed inline yet
for regular service.
Ray WA7ITZ
> Date: Sun, 10 May 2009 09:08:51 -0700
> To: amps@contesting.com
> From: romers@shaw.ca
> Subject: [Amps] FL2100B questions
>
> I'm working on a somewhat defunct 2100B for a blind friend of mine. He
> drives it with an old TS520. My pal tunes both his exciter and the amp
> with separate aural RF driven indicators. I've watched him do this
> many time and checked it out after, and he's always very close to
> right on. He operates only CW. I know squat about the 2100B, but have
> reasonable experience amp experience with my home-brew 813's.
>
> Problem: Over time the input swr to the amp appears to have gone
> haywire: 4:1 or more on 40; 1.8:1 on 80; less than 1.5:1 on 20. I have
> it on the bench here now and am driving it with my pro3. I can reduce
> the input swr to acceptable levels with a small antenna tuner between
> my exciter and his amp (or with the tuner in the pro3). The amp's
> output is fed into a dummy load with a known watt meter.
>
> Then, tuning up as per the manual for max power out, at the very best,
> with 50w of drive I can get a bit more than 250W out into a dummy
> load. Advancing the drive further and retuning doesn't produce a whole
> lot more output -- it appears to be saturating after 50 or 60W of
> drive (probably drawing lots of grid current). Plate voltage is OK.
> The loading control is all the way meshed on 80 and 40. It's seems
> quite normal on 20, but less power out.
>
> I didn't want to retune the input coils if the tubes were obviously
> bad. I can't get anywhere near 500ma of plate current needed for full
> output -- more like half that is about it.
>
> Is there anything else to look for before I look for new 572B's ?
>
> Thanks for any suggestions...
> Jerome - VA7VV
>
>
>
> --
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