[time-nuts] HP5370A self test fault characteristics and diagnosis

Robert Atkinson robert8rpi at yahoo.co.uk
Fri Jun 19 02:54:24 EDT 2009

Hi Bruce,
I once had a similar problem with AD595 theromcouple IC's we had a whole bunch of them on a car when suddenly 2 at the rear kept failing. After the third failure I investigated further and it looked like on all 3 the feedback pin(8)had gone open circuit. I prised them open and on each, the bondwire had broken. We put this down to noise levels or possibly local supersonic buffeting exciting a resonance in that particular bond wire. A "blob" of high temperature RTV on the chip seemed to cure the problem. Hermetic packages have their own issues.

Robert G8RPI.

--- On Fri, 19/6/09, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:

> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: [time-nuts] HP5370A self test fault characteristics and diagnosis
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Date: Friday, 19 June, 2009, 5:53 AM
> For the benefit of HP5370A and/or
> HP5370B users I have added a webpage
> detailing the characteristics and diagnosis of a fault that
> my HP5370A
> recently developed.
> With the 10MHz rear panel output connected to both inputs
> it developed
> an overange error when set to measure the time delay
> between the START
> and STOP inputs.
> Details are on the  web page:
> http://www.ko4bb.com/~bruce/HP5370_Faults.html
> <http://www.ko4bb.com/%7Ebruce/HP5370_Faults.html>
> At Didier's suggestion I've also included a link detailing
> the imaging
> setup and camera settings etc used to acquire the chip
> image on the
> above page.
> Whilst it is possible to obtain good quality images with
> less precise
> multiaxis positioner than those used, at least it is very
> easy using
> such equipment
> The chip image confirms the diagnosis inferred from
> measurements of
> various signals within the 5370A.
> Replacing A22U21 cured the problem,
> Bruce
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