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HP8563E - 100MHz VCO failure on A15 rf Board

Question asked by DomiB on Mar 30, 2014
Latest reply on Apr 1, 2014 by DomiB
Dear all,

I have an issue on a HP 8563E Spectrum Analyzer. The 100MHz VCO on the A15 rf Board doesn't oscillate (measurement made at output of the VCO with strap on TEST position). I am sure the VCO is faulty, the PLL loop must work.
Power rails (+/- 15V) are fine.
I have checked the active components (without de-soldering) and none of them seem faulty.
Adjustment of C750 capacitor doesn't bring anything.
I would be happy to know if somebody has already experienced (and solved) such failure or if  a component of the VCO is prone to fail ...
I have almost all the VCO active components in spare parts (except the 100MHz xtal) , but before de-soldering on the rf Board, I would be very happy to have your advice.
Thanks for reading and for your help.