Re: 2710 Spectrum Analyser 'Cannot count VCO, IF' error


Martin Whybrow
 

I've done some probing and have identified a problem; note that mine is a post B010318 model, so it has the CFCS rather than the CFC board.
I have a very low signal level at J130 on the Phaselock Assembly (beat frequency output to the counter); the manual indicates this should be TTL, but it's about 100mV peak to peak. All of the supply lines are in limits, but I'm not seeing any signal gain between J110 (Phase/ Beat signal input) and the output of U720, with ~150mV p-p signal levels at each stage.
I have noted that there are some mods to the board and I'm not sure if thas has any bearing on it, I spotted that C742 and C747 have been removed and a through hole 220nF fitted instead, so this may be a repair to deal with a damaged track.
If anyone's familiar with this assy, I would appreciate your suggestions.

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