teexmmo@ioe.lon.ac.uk (Matthew Moore) (07/23/90)
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?
rbn@umd5.umd.edu (Ron Natalie) (07/24/90)
More likely it is one of two problems that I've seen frequently with the MCA cards. The most common is the prepensity for the cards to lever or see-saw out of the slot due to the complete lack of any kind of mechanical design to hold the cards in the right position. The other is that some misdesigned cards will extert stress and sometimes even break the card edge connector by sliding the card out the end. -Ron
nathan@yatton.inmos.co.uk (Nathan Sidwell) (07/24/90)
In article <1990Jul23.142511.15070@ioe.lon.ac.uk> teexmmo@ioe.lon.ac.uk (Matthew Moore) writes: >Does anyone know what the effect of mechanical stress on an MCA board >would be? > [describes problems with PS/2 70 & 55X] I had a similar problem with a PS/2 80. When developing a card, it would work fine with the lid off, but sometimes not when I put the lid on. The problem was not just with my card, but with the memory expansion too. It appears that the foam packing on the lid, which is supposed to hold the cards in tightly was overzealous, and pushed down on the card handle, thus levering the other end of the card out. The solution was to cut away the offending bit of foam. It has worked fine for the 2 years since then. Foam pressed here V +--+ +---------------------+-+| | ++ | | | | +--|||||||--------------+ --------------- So what's your mission statement? ---------------- Nathan Sidwell, INMOS Ltd, JANET: nathan@uk.co.inmos Aztec West, Bristol, UK UUCP: ukc!inmos!nathan My indicision is final (I think) INTERNET: nathan@inmos.com