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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