Title       : Yaesu FL2100B PI-filter !!

YAESU FL2100B
Input PI-Filter RE-Work

This linear was designed for a tube type driver.  If you have been using
it with a transisterized exciter, it was necessary to utilize a tuner
between the exiter and the linear.  Without a tuner, it would drive the
ALC of the exciter wild..  sometimes to the point of exciter shutdown!

I completely reworked the input PI filter of the linear to obtain a
better match.  It sure paid off.

1.      Remove all capacitors and the wires from the waferswitch from
        the input coils.
2.      Remove the capacitor C220 from the filament of the final and
        replace with a 0.01 disc 2kv.
3.      Disassemble the 80 meter coil and rewind it with 2 extra turns
        for a total of 14 turns.  Use #18ga wire.   Reinstall.
4.      Disassemble the 40 meter coil and remove one turn.  Reassemble.
5       Disassemble the 10 meter coil and remove one turn.  Reassemble.
6.      Rewire the coils to the waferswitch.  Do not mix input and
        output connections.
7.      Form and bend a #10ga bare copper wire from the ground lug of
        the final tube towards the coils at a height of ½ inch over the middle
        of the coils and back down to the other ground on the tube socket.  
        This wire is used to ground all the new capacitors from the coils.
8.      Change all capacitors as follows and replace with 5% 500volt
        Silver Micas.
                INPUT                              OUTPUT
        80 meters 1300; was none                1000; was 1000
        40 meters  820; was 500                  500; was  400
        20 meters  470; was 350                  270; was  250
        15 meters  360; was 250                  220; was  200
        10 meters  220; was 200                  180; was  100
9.      Connect a good SWR meter between exciter and final.  With very
        low drive, just enough to get an indication on the meter (5-10W) adjust
        the final for approximate tune and load positions, adjust the coil slug
        for minimum SWR.  Now increase drive and load the final for normal
        output.  Ajust again for minimum SWR with the coil slug.  Repeat this
        for all bands.

In my case the worst reading was on 80 meters with a 1.6:1.  All other
bands were much better.  Reports have been very good and the general
comment was that the audio was much crisper and cleaner.

73, Werner/AA4IX@N4CII.#CHS.SC.USA.NOAM
(Werner Dolder, 327 Heber Rd., Summerville, SC  29485-4608)

DOWNLOADED AND REALIGNED FROM THE PACKET NETWORK BY BOB G0LBQ - N6XDI.