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1040STf ground issue?

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Hello all - Been a lurker for awhile, but decided to post after not being able to figure out an issue. I recently picked up a cheap "working" 1040STf from eBay. The guy packed it fairly poorly, so I wasn't surprised when it didn't turn on. However, when I went to move it from the left side front corner, I suddenly heard a noise like power was being supplied, and the light when on. Lo and behold, the thing turned on and I could hear the FDD working. When I set it back down, it shut off..


I took it apart and cleaned some areas and looked around at the mobo for bad traces or leaky caps and there were none that I could (shockingly). I ended up installing TOS 1.4 chips while I was at it. Tried it again, and the same issue occurs where I have to lift the front left corner up for it to work.



  • Unit only turns on when lifting the front left corner
  • Will stay on for hours like that, and sometimes I can remove the object from the corner and it will stay on, but usually it has to stay lifted
  • I checked around the PSU (including the switches and IEC port) for any issues with a multimeter and couldn't find any off hand
  • I looked for any metal touching in places that shouldn't, but couldn't see any in that area
  • MOBO is rev A!


I noticed there's no plastic or anything beneath the PSU frame, and they look very close to the TOS eproms - could that be an issue? I'm going to tear it down again and check out some things in that area. Is the RF shield 100% needed?


Thanks for reading!

Edited by formdissolve
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2 hours ago, snarkdluG said:

You don't need the shield at all.


It could be a crack on the main board or just IC creeping out of their sockets. Try pushing them down or better, cleaning them first with IPA or contact cleaner and then reseat them. 

Thanks, I'll inspect the board again. I've done a deoxit job on the power socket and tried multiple cords, but that hasn't helped. I'm leaning towards some traces or something that need to be re-soldered.

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