[R-390] R390A 2nd LO subchassis oscillator issues

[Larry H]

Hi Alan,  I think your right about the crystal.  Did you try adjusting the 7-24 cap?  And, did you try re-seating the crystal?  Do you have another you can try?

Regards, Larry


On Saturday, September 20, 2014 2:59 PM, Alan Victor <amvictor at ncsu.edu> wrote:
 


Good day. Have an R390A with poor sensitivity on some bands and quite fine
on others. Cam alignment and PTO run out look good. 17 MHz xtal running
well with 7-9 V p-p RF output at the injection port to the 1st mixer.
However, on 7 MHz, the required 3rd harmonic is way down in level and the 7
MHz sensitivity is hard hit. However, on 15 and 24 MHz poor sensitivity but
not nearly what it is on 7 MHz. Meanwhile on 21 MHz, better than 0.15 uV !
So I am suspecting a very aged low activity 9 MHz xtal and probably a dirty
bandswitch in the 2nd LO subchassis as well. As far as I can tell the
mechancial line up looks reasonable but the RF-electrical issues are
clearly more evident. Before I attempt to do any mechnaical alignment, I
think it makes sense to fix the OBVIOUS electrical shortcomings, like low
LO INJECTION level on the 2nd LO subchassis. Any ideas ? Tnx, Alan W4AMV.
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