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On Mon, 15 Apr 2024 13:05:40 -0700, john larkin <jl@650pot.com> wrote:
>On Mon, 15 Apr 2024 15:41:57 -0400, Joe Gwinn <joegwinn@comcast.net>>
wrote:
>On Mon, 15 Apr 2024 10:13:02 -0700, Don Y>
<blockedofcourse@foo.invalid> wrote:
>Is there a general rule of thumb for signalling the likelihood of>
an "imminent" (for some value of "imminent") hardware failure?
>
I suspect most would involve *relative* changes that would be
suggestive of changing conditions in the components (and not
directly related to environmental influences).
>
So, perhaps, a good strategy is to just "watch" everything and
notice the sorts of changes you "typically" encounter in the hope
that something of greater magnitude would be a harbinger...
There is a standard approach that may work: Measure the level and
trend of very low frequency (around a tenth of a Hertz) flicker noise.
When connections (perhaps within a package) start to fail, the flicker
level rises. The actual frequency monitored isn't all that critical.
>
Joe Gwinn
Do connections "start to fail" ?
Yes, they do, in things like vias. I went through a big drama where a
critical bit of radar logic circuitry would slowly go nuts.
>
It turned out that the copper plating on the walls of the vias was
suffering from low-cycle fatigue during temperature cycling and slowly
breaking, one little crack at a time, until it went open. If you
measured the resistance to parts per million (6.5 digit DMM), sampling
at 1 Hz, you could see the 1/f noise at 0.1 Hz rising. It's useful to
also measure a copper line, and divide the via-chain resistance by the
no-via resistance, to correct for temperature changes.
>
The solution was to redesign the vias, mainly to increase the critical
volume of copper. And modern SMD designs have less and less copper
volume.
>
I bet precision resistors can also be measured this way.
>
>I don't think I've ever owned a piece of electronic equipment that>
warned me of an impending failure.
Onset of smoke emission is a common sign.
>
>Cars do, for some failure modes, like low oil level.>
The industrial method for big stuff is accelerometers attached near
the bearings, and listen for excessive rotation-correlated (not
necessarily harmonic) noise.
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