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IIci carcass with VERY unstable video


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I have a IIci carcass (PSU, Motherboard, 8MB Memory, Floppy drive, no cache, no hard disk) with VERY unstable colour.  I've verified that it's not the PSU by swapping in a known-good PSU - and the problem persists. There's no sound either, if it comes to that. I've verified that it's not the monitor, by plugging in a known-good IIci - which displays a clear, crisp, image.  The faulty IIci? That's a different story.

In the first instance, the image takes a very long time to appear - and then it fades in and out, and the colour flickers with a distinctly purple hue.  Eventually, it decides that it wants to boot - and presents a flashing question mark disk (as you'd expect).  I don't know whether it actually would boot though, because the floppy drive seems jammed and doesn't want to inject a disk.

So… Before I put it on eBay and write it off as a dead-loss, does anyone have any idea what might be amiss?  I'm guessing caps (none appear to be leaking, there's no goop on the board) - but which ones could be responsible for a fault like this?  I suppose that it does have some value still, even if only for the PSU, memory and case.

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Posted (edited)

If you have no sound and video is unreliable, your logic board needs to be recapped to start with. Replace all electrolytic SMD caps with new ones, you can use equivalent replacements or tantalums. Just because they don't look like they are leaking doesn't mean they aren't.

 

Also post some good photos of your board if you can please, we might be able to spot any other issues.

Edited by joshc
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