Sb-220 power output at about half..

[Roy Morgan]

At 11:33 PM 5/24/2007, John wrote:
>...The plate air variable was really sensitive to me
>until this happened. Now it seems that the plate has to be turned quite a
>bit off of peak tune position to cause the peak output to change a little.
>The best tune position on the plate variable also seems to be with the
>plates open, in other words I am saying they don't overlap any to me as it
>seems to me it should.

Yes, they CERTAINLY should overlap at lest a little bit.. the tuning of the 
final tank circuit has changed.  Look for these possible things:

- If the plate tune cap is a double section one, check all connections to 
(both) sections.

  - The bandswitch adds a fixed capacitor at the loading cap for 80M 
frequency operation, check the bandswitch contacts and also that 
capacitor.  (This cap is to the left of the Bandswitch Wafer 2 in the fuzzy 
diagram I have.)  If you have to replace that cap: make sure you get one 
rated for high RF current, or it will blow up.

- Check any bandswitch contacts that change coil taps

  - be sure all connections to the final tank coil are good (solder and any 
connections made by screws or nuts.)

  - Make sure no turns of the tank coil are shorted.

It's possible some thing has shorted in the filament RF choke.

Have you tried operation on a higher band?

Try tuning the input circuit (though your symptoms don't point in this 
direction).


Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911   Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-975-6097
roy.morgan at nist.gov --  

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