Thread: SB-200 Help
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Old November 19th 04, 04:47 PM
N0DG
 
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Tom,
You did not give a lot of information but! assuming the high voltage to be OK
(aprox 2200 volts) and the tubes good. The operating bias on the grids is set
by the voltage droop across the relay coil in parallel with R18 a 2k resistor
and voltage divider resister R16 (33 ohm). this assumes that the bottom of R16
connected to the antenna relay jack is shorted to very near zero volts when you
key the rig. Bear in mind that the transmitt relay or transistor in your
xceiver must sink quite a lot of current. If the Relay or transistor in your
rig have resistance (pitted contacts ETC.) this resistance is in series with
R16 and could easily change the bias voltage to drop the idle current and also
the amount of drive required for the amp.

My guess is that if you relay jack to ground you will see the idle current jump
to the recommended 60 ma. Use caution as the jack has -160 volts DC on it and
enough current to really give the relay's in modern rigs a work out. You might
need to add an external keying relay.

good luck with the trouble shooting.
N0DG Don