I redid all the Alignment and Test, Part II steps starting on pg. 63, plus
checked the VCO frequency at the low end of each band against the chart at the
lower left corner of the Schematic Key sheet in Appendix B of the manual. In
doing all that, I re-ran the VFO Linearization (which my notes show that I
successfully ran on 10/28/08).
Everything tested out correctly, except that on the VCO frequency test my 60m
and 30m numbers were a bit beyond the +/- 40KHz that Don suggested. However, I
ran this test before I re-did the PLL linearization, so I need to re-run it.
After finishing the tests, I'm now getting a change in pitch as I tune across a
signal. In addition, I can now hear things even with filter 4 in use. I guess
that I somehow managed to get the PLL un-linearized while I was finishing the
build and doing the Part III Alignment and Test. Not quite sure how I did it,
but never put it beyond my abilities to do something like that ...
Given that AGC was mentioned by both of you, I also re-ran the "Setting The AGC
Threshold" on page 48. I could not get a reading of 3.8 volts on pin 5 of U2.
The best I could get was just over 3.5 volts. I see from my notes that I had
to crank R1 all the way to get 3.8 volts when I did this test a couple of weeks
ago. Looks like there's an issue there.
I'm still getting a situation in which a stronger CW signals will completely
wipe a weaker one I tune across the band if they're close to each other in
frequency. Thus, I'm still getting that effect of a signal either being there
or not being there, with a very narrow bandwidth on signals that are close to
each other.
Unfortunately, the people who pay me a salary actually want me to do some
useful work for them, so I haven't been able to explore these problems any
further. I was going to check components in the AGC area plus check my solder
joints, make sure I haven't reversed anything, check the voltages per Appendix
E, etc., but that might have to wait a day or two.
One thing -- when I was building the set, I did notice that the resistance of
pins 7/8 and pins 9/10 of RP5 was not 470 ohms AFTER I mounted RP5 on the RF
board. I just don't see from the schematic why I wouldn't be getting 470 ohms,
but I'm relatively new at reading schematics. Those two pin sets are used in
the AF Amp, so it's not clear to me if that would have anything to do with my
problem.
Thanks for your help so far. If you have any suggestions that would help me
short-cut some of the testing, I would appreciate it.
Jon
KB1QBZ
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