When it is very warm in my shack (~85F) my Omni VI+ has the following problem
on 30M only.
Every 35 seconds or so the frequency would jump on the order of 10-50Hz for a
fraction of a second, and then return. The symptoms suggest that the 30 meter
L.O. (on L.O. mixer board) is briefly losing lock with the reference oscillator
(on logic board). At elevated temperature, I suspect that Y4 may drift
slightly out of spec; the DC voltage fed back through connector 84 then
corrects the oscillator frequency and regains lock. Perhaps an adjustment of
30M oscillator coil L19 would mitigate the problem.
If the problem starts occuring more frequently I may want to slightly adjust
L19 on the L.O. mixer board. However, my question is how to access L19 while
keeping the 30M oscillator active. The L.O. mixer board is located under the
FM and LL driver/NB boards, requiring disconnection of cables to access the
board.
I recall some discussion on the forum a while back about a similar 30M
instability problem. I appreciate any suggestions about how to access the L.O.
mixer board, while at the same time keeping the L.O. active. I did access the
L.O. mixer board to fix an earlier problem related to an L.O. output filter,
but totally removed the board at that time.
73 Jack K1VT
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