[Amps] FL-2000b tuned input problem

[Kevin LaHaie]

Hello Amps list.

I couldn't resist picking up an FL-2000b amp for 50 bucks.  Overall, 
clean.  Needed new diodes, had 3 new electrolytics.  HV now  2400v.  T/R 
Relay needed cleaning.  Works fine now.  Put a brand new matched pair of 
RF Parts 572b's in it.  All was well, almost.  I did perform the 
requested tuned input tweaking 'if the tubes were replaced with a 
different manufacturer'

I was unable to obtain a very low SWR on most bands, 10m being the worst.

On the good best band, 20 meters, it had amout 2:1 SWR and put out over 
500 watts into dummy load, on air QSO confirmed it was clean.

BUT, on all the bands tuning the plate circuit causes the SWR TO THE 
EXCITER to vary WILDLY.  Of course, dip the plate - lots of SWR at the 
exciter (IC756) which folds back power at the same time.  Little output, 
as you can imagine.

I have checked and cleaned verified the switching and components in the 
input circuit, only thing changed from stock was the value of the 10m 
capacitors (to lower values) but everything else is 'stock'.

Any ideas why the exciter would see a fluctuating SWR when the tank 
circuit becomes resonant?  I have used the exact setup on many other 
amps with no anomolies such as this?

Thanks for any suggestions!

73 de Kevin K7ZS



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