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[AMPS] Questions about FL2100Z and FL2100B Amps

To: <amps@contesting.com>
Subject: [AMPS] Questions about FL2100Z and FL2100B Amps
From: km1h@juno.com (km1h@juno.com)
Date: Fri, 6 Nov 1998 12:18:03 -0500

On Fri, 06 Nov 1998 14:44:57 -0500 Roger Stimson <K8rs@acd.net> writes:
>
>     Here are some questions for you amp gurus about a Yaesu FL2100Z
>that I am checking out:
>
>     On 10M  with 96 watts input, output is 320 watts, on 15M it is 
>473
>watts, on 20M it is 595 watts, on 40M it is 586 watts and on 80M it is
>640 watts.  Is this an indication that the tubes are going soft?


Possibly...that is a typical scenario.

>
>     With a Yaesu FL-2100B using the same test setup, 10M output is 
>600
>watts with 62 watts input.  I am using a Bird 43/1000H into an 
>Ameritron
>ADL-2500 dummy load and a Kenwood TS 950SDX as the exciter.


That is the normal power to expect with good tubes.

>
>     When I test the input power on "Standby", I get a marked 
>difference
>between the two amps.  The FL-2100Z shows a maximum output from the
>Kenwood  of 96 watts, but the FL-2100B shows a maximum output of 120
>watts.  Does this suggest that one or both of the relays in the 2100Z 
>is
>dirty/pitted?  However, the reflected power on both amps is 1.5 watts.

There is only one relay in the RF path. I would certainly start by
cleaning the contacts. Also look at the output connector, I have seen
several that have overheated and become a carbon resistor.

>With no drive the current is 0.100 amps on the 2100Z.
>
>     The tubes in the 2100Z are RF Parts.  The tubes in the 2100B are
>Centron.  Are my results showing the differnce between the tubes?  The
>FL-2100B had not be used much by the owner.  I can only guess that the
>2100Z had been given a lot of use given the changed tubes.

You can put the Cetron in the Z but DO NOT put the RF Parts in the B
without first modifying the bias circuit. 
That holds true with all ( "almost all" since there are so many Chinese
versions it is impossible to keep track) Chinese and Russian 572B's. They
have a bit higher gain and the stock bias is not sufficient to cut them
off in standby. The Yaesu/Svetlana mod bulletin is OK with Chinese but
somewhat marginal with Svetlana. 
I have written up a bias mod that provides -125VDC for full cut-off as in
the SB-200.
Parts are cheap at Mouser and RatShack. Send me a SASE if you want a
copy.

73  Carl  KM1H


>
>     I would appreciate any and all ideas that might account for these
>differences.
>
>     Thanks,
>
>                  Roger Stimson K8RS
>
>
>
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>
>

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