On Thu, 11 May 2006 06:18:28 -0400, Jay W. put
finger to keyboard and composed:

Hello folks,

I am having a rather unusual problem with about six hundred embedded
motherboards in the field, and was hoping someone might have an idea (or
two) on what might be happening, and possibly what the fix might be.

These are embedded low power Via C3 based motherboards that are deployed
in the factory automation industry. Power is distributed from the power
supply to the motherboard through a 12" power cable which consists of (2)
18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on
the motherboard; the board draws about 3 amps of +5VDC under maximum CPU
load. After several months in the field, contact resistance on the ATX
connector increases for some reason, and is causing a voltage drop as seen
on the motherboard (sometimes as much as .5VDC!) There is an onboard
voltage monitor on the CPU board that triggers a reset at about 4.7VDC,
the end result being that the processor gets stuck in a reset loop - it
will run for a minute or so and then the CPU load momentarily increases
and resets again. The voltage drop is *usually* greater across the ground
lines than the +5 lines for some reason. Maybe there's a clue there?

On a system that is failing, unplugging the ATX connector and reseating it
will "fix" the problem and the system will continue to work for several
months until once again the resistance increases in the contacts and...
well, you get the picture.

If the connector is reseated here at the factory and "repaired", we cannot
get it to fail again under any conditions: vibration, humidity,
temperature cycling in a environmental chamber, etc.

We've tried using contact lube - no luck.

If it's an environmental issue, try flooding the connector with the
same gel (?) that telco's use for their wire joins. Or try vaseline.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.