[time-nuts] HP 5372A troubleshooting

Adrian rfnuts at arcor.de
Fri Jan 29 16:58:13 EST 2016


Morris,

you might want to download the 5371A service manuals which contain
schematics.
The 5372A being an 'upgraded' version of the 5371A, most of its parts
are identical.
Look for 05371-90018 (Vol.1) and 05371-90034 (Vol.2).
They should be available at www.keysight.com
The scan quality is surprisingly good.

The A10 regulator board is in Vol.2 on p. 7I-9.
The -15 are generated out of the unregulated +25V by a switch mode
regulator, so there should be much less (40kHz switch frequency) ripple
than described.
Otherwise the obvious electrolytics are to be suspected (in particular
C17, but also C7, C24).

Regards,
Adrian


Morris Odell schrieb:
> 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?
>
> and
>
> 2. Has anyone had to deal with this this problem before?
>
> Thanks,
>
> Morris
>
>
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