Carl, I am having an experience similiar to yours, except on an
FL-2000B. The only tubes I have are RF Parts Taylors, a matched pair
which I am pretty sure also are chinese in origin, and would share the
design differences to the Cetron 572B.
For the life of me, I cannot get the SWR adjustments anywhere near where
they should be, 20 meters is OK but the rest just refuse to co-operate.
I also get a fluctuating input SWR as I tune the finals, which may be
something else, but adjusting the slugs per the technique in the manual
is fruitless.
So, I think you are on to something there. Thanks for sharing it! If
you find a solution, please post it here!
73 Kevin K7ZS
c. wrote:
> I have made an interesting note on the FL2100B input swr VS.
>tubes.!!!
> I have been fighting this amp for a long time now using chinese
>tubes and could never get the input swr down much below 2.5 :1.!!!On 10
>mtrs. I had to add capacity to the input pi-net to get anywhere near
>even 2:1. !!
> I recently acquired a pair of Cetrons, ( 572B/T160L ) , which
>I think was the tube originally used in that amp.
> I tuned the inputs per the original instructions and lo and
>behold, the inputs are almost all well below 1.5:1 swr. the only
>exceptions are the high end of 80 ( 1.55:1) and the High end of 10 (
>29.4 -29.7 , 1.45 :1 , !!!) I also had to remove the extra capacitance
>I had added on 10.
> I have to wonder now about the actual input capacitance of
>the chinese tubes !!!!
> what ever it was that caused the problems on 10 mtrs. I will soon
>see if it has gone away.!!!!!
> Has anyone else had problems with the 2100 on ten mtrs ??
> Just wondering.!!!!
>
>
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