> John,
> For the time being (until you solve the current problem) the only voltages
> at U6 that matter are pins 1, 2 and 3 - and those are correct. The other
> pins will likely fall into line after you have this problem fixed and if not
> there is another problem with the VCO.
> Right now, the voltages being fed out of U6 pin 1 are correct for the
> stimulus you provided (CAL FCTR and tapping BAND+ and BAND-). Now check to
> see if that (proper) 0 to 8 volt swing between pressing BAND+ and BAND- is
> carried on through R19 and then through the RP2 sections and then onto the
> cathodes of D16 and D17. If you get a decent voltage swing between BAND+
> and BAND- (you can expect a bit of voltage drop on the 8 volts end) at the
> varactor cathodes, then look for something else wrong in the PLL Reference
> oscillator (upper left of the schematic sheet - but only as far to the right
> as TP3), the PLL chip does not matter until the PLL Reference oscillator is
> functioning properly.
> If you do get a good voltage swing at the varactors, then all I can say is
> either Q19 oscillations quit when the varactor capacitance is reduced, or
> there is something wrong at C84, C85, D17 or D16 which is stopping the
> oscillation. If you suspect Q19 itself, you could try swapping it with one
> of the J310s on the Control Board at Q6 or Q7 (these in a less-critical
> audio circuit rather than being used as an RF Oscillator).
> 73,
> Don W3FPR
Everything checked out okay, so what I think I'll do is to replace D16, D17, Q19, and the caps. Thanks again for all of the help, and I'll be back in a few days (after I get the new parts installed) with hopefully a working radio.
Thanks again,
John
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