[AMPS] FL2100Z problems

[Darren Collins G0TSM]

>The other thing I noticed was that moving the tune and load control around
>reduces the anode current suggesting oscillation.

This happened to my FL2100B. I built a pcb using the biasing circuit from
the Z model but the amp still oscillated. I found the answer in the
archives of this reflector. It turned out that valves/tubes weren`t seeing
a load due to a hairline crack in the ceramic HV blocking capacitor between
the valve anodes and the tank circuit (whatever it`s proper name is). This
obviously didnt show up with a multimeter but the capacitor fell apart when
I stripped the amp right down.


The mod that is at RF parts is not needed on the `Z` models as the
increased negative bias during standby prevents self oscillation.. 

73 Darren







http:www.qsl.net/g0tsm/


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