Gentlemen,
I've completed the GI7B conversion of a Dentron GLA1000. I've added the
tuned input board, rewound the output tank coil, built the cooling
enclosure, redone the bias , etc. On 40 and 80, all is well, and the amp
works as I'd expect. On 20m, it also works well, but when I advance the
drive beyond about 25 watts, the amp takes off (plate current rises, output
power rises) and if I don't get the exciter off quickly , there's an arc in
the tune capacitor. The conversion was modeled after that of N8GPQ.
I've rewound the "parasitic choke" (47ohm 2watt resistor w/5 turns), with
no effect, and wonder where to go next. I've really learned a lot with this
conversion, and it looks like I'll learn some more as I try and track this
phenomenon down.
Where would you go first, if trying to chase down this issue? Since I
built the thing from a bare chassis, I'm not afraid of digging in.
Thanks for any pointers
John K5MO
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