You likely need:

• ...to get a better PSU. Neither of those units you've tried are particularly high-quality.
• ...to replace the capacitors on that board. Bad caps can short, causing the symptoms you describe.
• ...to check mundane things like too many motherboard standoffs, which can short out motherboard traces and also cause the symptoms you describe.

gladders wrote:

Hey all, novice computer builder here fighting some gremlins. […]
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Hey all, novice computer builder here fighting some gremlins.

I'm trying to build a W98 machine with the following components:

epox ep-4pda3i motherboard with Pentium 4
2 sticks of 256MB PC3200 RAM (so 512MB in all)
NVIDIA GeForce 4 MX460
Soundblaster Live

However when I try to power it on, the CPU fan jolts slightly and then doesn't move. Removed the GeForce, same. Removed the RAM, same.

So, I figured the PSU was busted - it's pretty ancient. So I went to my local PC components shop, picked up another.

So instead of a Sparkman SM-350-12-DL outputting 100W (I think), I now have a Colorsit ATX12V P4 outputting 400W.

Sadly, no change. There's two different versiions of the 4-pin breakout ATX connector, and one caused the fan to move noticeably more than the other, but also stopped within a second.

I really hope the motherboard isn't fried 😕

Any help please?

Post up your own clear photo of the motherboard.

Depending on the revision, you might either have Rubycon caps or cheap Teapo crap.

Pray it to be the former, or else you have a short on 12v. If it's the latter, you'll likely get away with just a full recap of the motherboard. In the case you have Teapo caps, try sourcing Rubycon caps (or Panasonic, your choice), these guarantee you another good run of your board.

Teapo are by far not the worst you can use, although they're certainly less desirable in low ESR applications. Having said that, the board is from the era of capacitor plague and Epox were known to have issues (although their boards were also sometimes resistant towards operating problems due to failed caps, probably by over engineering).

Panasonic and Rubycon are good replacements, as are Nichicon, UCC/NCC, Suncon, etc. The components should ideally be matched to what they're replacing in terms of performance parameters.

Hi, OP here.

Not sure what happened, but I fiddled with the pin connectors for the front panel stuff, and retried the 4-pin connectors, and it suddenly works. Weird.

Now to figure out why it thinks the drive has bad sectors. Thanks for the advice all.