[time-nuts] 3.0GHz Channel 3 installation in Agilent 53132A counter

James Robbins jsrobbins at earthlink.net
Wed Mar 19 11:26:39 EDT 2014

Thanks for everyone's help here.  I have done some further sleuthing.

I have a second 53132A which has a 3.0GHz Channel 3.  So, I switched the new channel 3 board into the old 53132A and it reads properly.  Then, I switched the old 3.0GHz Channel 3 board into the new 53132A and it also read four times (4x) the input frequency.  From this I conclude that the issue is with the new 53132A counter box and not the channel 3 board.

Then I powered up each counter and measured at the pins on the ribbon cable connector at the Channel 3 board to the main board on both the new and old counters (channel 3 boards plugged in and powered).  They each read the same voltages and/or grounds (pin1 = 2v; 2,5,7,9,10 = ground; 3,8 = +12v; 4 = -12v with numbering based on "1" shown on channel board).

Someone suggested that maybe the new main board had been set up for the 12.5 or 6GHz channel 3 but was sold without that channel.  The idea was that such a main board would cause a 4x reading.  To my mind this is opposite to what I would think in that the division ratio for 12.5 or 6GHz would be higher than the ratio for the 3.0GHz board and would result in a fraction of the frequency rather than 4x frequency.  

Of course, it could be a FW mod (rather than a HW mod) which has been applied also.

Any other thoughts are much appreciated.

Jim Robbins 

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