. It appears to me that It's picked up some
added capacity on 40 and 75
meter positions and thats the reason the plate tuning capacitor is tuning to
less capacity ( 20 mtr.area ) for resonance in the 40 and 75 meter bands. I've
checked about everthing, I've cleaned (ink eraser) and completely checked the
band switch (continunity), removed and checked the values of the plate
blocking cap C24, 1000uuf, C26, 100uufd parallel cap, and the 500uufd
switched in
loading cap for 75 mtrs. All were within 10% on my cap. meter. I lifted the
1.1
mhy. RF choke and output lead to check the loading cap. tested perfect. With
the plate tuning cap fully meshed ( max. capacity) attached to the total turns
of the coil assy. the capacity reading was 215 uufd, with the plates fully
open the reading was 65 uufd verifying that the plate tuning cap was at it's
proper value of 150 uufd. My questions are ---
1. Is 65 uufd a reasonable amount of stray capacitance for just the final
coil assy ?
2. Does anyone know if there is a minimum capacitance value for the plate
tuning cap ?
3. Any suggestions / help would be much appreciated.
If you are sure it is not the padder caps changing value when power is applied,
I would check for shorted turns on the plate choke, and its bypass cap. It is
hard to trouble-shoot via E-Mail! While you are at it, unsolder one end of each
resistor on the parasitic suppressors, and make sure they have not changed
value. I do this at annual spring-cleaning on my amps religiously.
GL!
Phil, K5PC
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