[Amps] FL2100B questions

[Alek Petkovic]

Hi Jerome,

Very common symptom with the FL-2100B. It is the 40m input tuning 
network capacitor/s. They are nice big brown, heavy duty looking iems 
but they are known for their high failure rate. I don't have the 
circuit in front of me but I think the 40m ones are around 400pF - 
500pF. Replace with a good silver mica cap of the same value and 
you're back in business.

73, Alek
VK6APK


At 12:08 AM 11/05/2009, jerome schatten wrote:
>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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