Bill,
Voltage at the drain of Q24 will only appear during transmit, TUNE or when
you have selected CAL FCTR in the menu. Try it in one of these states and
see if you have a signal at TP2 - the expected level is in the 0.25 to 0.70
volts RMS range (if measuring with an RF probe) - if you are measuring with
a 'scope, multiply by 2.8 (or 3 for a quick estimate) to find the peak to
peak voltage.
73,
Don W3FPR
> -----Original Message-----
>
> Hi Group,
>
> I have been struggling for a month to figure why I have no BFO at
> TP2. Also, Q24 voltages measure zero all around. The gate has a
> very small (10 mV peak) distorted version of the nice sine wave
> on U11's nice 1V peak sinewave.
>
> I have traced all the way back to Control Board U8 pin 2 where V
> ALC - the bias for the drain of Q2 - derives, and that pin never
> leaves zero. U8 pin 2 is labelled V PWR, which is the bias and
> control voltage for Control Board U10 pin 3. Then the signal "V
> ALC" finally is sent to the RF board from the emitter of Control Board Q8.
>
> There is continuity between Control Board Q8 emitter to RF Board
> R98, the drain bias/AC decoupling resistor for Q24. Something is
> dragging down the bias for Q24, and I simply can't figure out why
> using two different RF boards, and now two Control boards.
>
> What would happen if I were to bias Q24 drain with a 2K or so
> resistor to 8 volts and see if we can check Q24 and V ALC in general?
>
> HELP!
>
> Bill
> NA7Y
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