[time-nuts] HP 5371A problem

Mark Sims holrum at hotmail.com
Fri Oct 3 19:12:55 UTC 2008

I have an HP5371A with a problem.  It fails the Input Amplifier test.
The error message says Bad Comparator: Result A: stuck low.

If you do a auto trigger level set,  channel A gives flakey readings.
When measuring the internal timebase signal (patching the back 
panel BNC to the input pods) "auto trigger" on channel A
sets the threshold around -1.2V,  channel B gives around -26 mV.

If you manually set the channel A trigger level it seems to work fine.
Changing the "A" threshold a few percent will give good readings.  This
makes me suspect that  the comparator hybrid may not be at fault.

Any ideas of what is going on or how to fix it? I did swap the card 
with another machine and the problem is with the A2 card.

Or does anybody have a spare A2 input amp card for a 5371A?  

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