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HP8753C won't phase lock below 16MHz with A9 CC jumper in 'NORM'

 

I'm trying to recucitate an HP8753C.
I replaced the YTO which was bad and was able to do the 'Source Pretune Correction Constants' adjustments procedure.
This is done with the A9 jumper in the 'ALTER' (right most) position. After adjustment the jumper is returned to the 'NORM' (let most) position.
When I do this I do not get phase lock below 16 MHz (low band).
The High/Low Band Transition Adustment shows normal (right hand trace ~150mv highr than left).
?Do anyone have a clue as to what might be wrong?? Why would the jumper position effect the performance of the PLL?
no lock below 16MHz with A9 CC in 'NORM'
With jumper in 'NORM' (.3 to 20MHz)

phase lock over entire range with A9 CC jumper in 'ALTER'
Jumper in 'ALTER' (0.3 to 20MHz)
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