Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!mcgill-vision!snorkelwacker!usc!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!aplcen!uunet!mcsun!ukc!educ-isis!teexmmo
From: teexmmo@ioe.lon.ac.uk (Matthew Moore)
Newsgroups: comp.sys.ibm.ps2.hardware
Subject: Effect of mechanical stress on MCA board
Summary: stress is apparent cause of POST fails
Message-ID: <1990Jul23.142511.15070@ioe.lon.ac.uk>
Date: 23 Jul 90 14:25:11 GMT
Reply-To: teexmmo@ioe.lon.ac.uk (Matthew Moore)
Organization: Institute of Education University of London
Lines: 23

Does anyone know what the effect of mechanical stress on an MCA board
would be?

Symptons: on two PS/2's (a 70/061, and the newer 55SX), failures
occurred during the POST, generating system board type failure (codes
starting with '1'). 
Following a check that boards etc were seated correctly, it was noticed
that the machines would boot up ok with lids off. The model 70 would
boot up with the lid on, but not when the VDU was placed on top of it.
On examination, it appears that the roof fouls (ie contacts) the
plastic handle on the top of bus expansion card for the disk drives.

The model 55SX exhibited similar symptons. The bus expansion card is
supported by a piece of black plastic which clips into holes on the
power supply. The new ribbon cable assembly passes between this and he
roof. On the 55SX examined, the roof fouled the cable assembly, and
hence the planar board, via the expansion card. When the black plastic
support was removed, the machine would boot up ok.

The assumption at the moment is that the POST failures are caused by
stressing the board. 

does anyone have any comments to offer?