I am converting an sb-200 for six only. All band switching was removed,
and only the 10 meter input coil was retained as well as a few turns of
the ten meter output coil. Rotor and stator plates have also been
removed from the tune cap. Harbach power supply w/ soft-start,
soft-keying assembly and new fan was installed. A new set of matched
Svetlanas were installed. A new set of parasitic suppressers for six by
Al Harbach were installed. (Nichrome, abt 1/2 turn w/ Panasonic
flameproof resistors) at right angles to each other. My PROBLEM. Help
please, I'm no EE, for sure Hi
1.) One of the tubes (it can vary) will go into serious
self-oscillation? (anode turns cherry red in seconds and throws circuit
breakers) w/o any drive at all (nothing connected to input) when I turn
the tune cap!!! Input and output coils are parallel and shielded from
each other, and cover is on when this happens. I also have an old set
of weak CETRONs and it will do the same thing with them.
2.) Can't get a low match on the input circuit. Used a MFJ-259B on the
input, closed the relay and have tried PI networks, L, all sorts of
changes to the coils, capacitor values and nothing gets it below abt 8.
to 1. Will it change much when powered up??
Thanks for any help and appreciate your time reading this. TU in
advance, Phil W2GE
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