[AMPS] big tube problems with yeasu Fl2100B, please help!!!!!!

[km1h@juno.com]

On Tue, 26 Jan 1999 23:59:59 +0100 "Theo Koning" <pa3erl@xs4all.nl>
writes:
>
>Hello and thanks for reading this,
>
>I have big problems with my yeasu fl2100b Amplifier.
>I have a pair of new tubes in it because one ore two tubes are getting 
>a red
>color, when I tune with low power ( 5 watts input).

DO NOT use Russian or Chinese 572B's without modifying the bias supply.
Those tubes will often oscillate even in standby.
RF Parts and Svetlana have modification info on their web pages. 


>The power output seems good only on the 80 meter band I can get a dip 
>or
>full power with the tubes.


Measure the R value of the parasitic suppresors. Replace if off by 10%.


>Also with one tube (572B) the onetube installed for testing is colored 
>red,
>With my old tubes I get the same problem as above.


Without any RF drive what is the idle current? You can check each tube
one at a time.

What is the input VSWR on 80, 40 and 20M ? 


>I have cleaned the bandswitch and the coaxrelais and all that is 
>okay.
>The resitors on both tubes are also new so that must be no problem.

The FL-2100 has been known to eat bandswitches. Are you positive of a
complete RF path??


>
>Do you recognize this problem, please send me an e-mail.
>
>Best regards from Theo PA3ERL


Get back to me please Theo.

73  Carl  KM1H


>=================================================
>Theo Koning PA3ERL
>
>Internet E-Mail: pa3erl@xs4all.nl
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