[time-nuts] HP 5372A troubleshooting

Morris Odell vilgotch at bigpond.net.au
Fri Jan 29 11:17:47 UTC 2016

Hi all,

I have been on a steep learning curve on my new 5372A. It's a lovely
instrument but does seem to have a higher degree of trigger jitter than I
would expect. Going on previous experience with other unrelated instruments
I began by checking the power supplies. (in fact it's hard to go much deeper
without the unobtainium extenders :-(

Anyway the power supplies all check out OK voltage wise but the -15 does
have a higher amount of twice mains freq ripple than the others. It's about
0.5 V p-p at the test point on the triple regulator board and looks like a
sawtooth i.e. what you see from inadequate filtering. The service manual is
unhelpful as it doesn't give schematics, just says to replace the regulator
board! The -15 features on the schematics for many other parts of the 5372A
that would be expected to contribute to trigger stability. 

My questions are:

1. Could anyone on the list with a functioning 5372A slip a scope probe onto
the -15V test point and check the ripple on a known good unit?


2. Has anyone had to deal with this this problem before?



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