Computer won't POST after motherboard/CPU being replaced as DOA

2

I got a bunch of computer parts recently (that's not quite complete, but is pretty much). It's currently plugged together sitting on desk in pieces, the motherboard sitting on its cardboard box, with the following things attached: MSI AM1I motherboard, AMD Athlon 5350 CPU, Corsair Vengeance LP 8GB (2 x 4GB) DDR3-1600 Memory, and a Silverstone SST-ST30SF PSU. All of those except the PSU got returned as DOA a few weeks ago, given I was unable to get it to POST.

I have now had these returned, with the motherboard and CPU replaced under warranty, and the memory returned as working. Put everything back together on desk, and still... nothing. No beeps, no fans spinning up (the PSU fan is unlikely to; the whole system even under full load should still draw sufficiently little power it shouldn't spin up), no nothing.

The PSU didn't get send back originally because attaching the PS_ON pin (of the ATX connector) to ground did cause it to start providing enough power for the disk to spin up (though unsurprisingly the PSU fan sat there idle), so on the face of it, the PSU does at least somewhat work. Prodding the motherboard with a multimeter shows voltage over the power-on pins (though that voltage causes nothing to happen), and over the CMOS clear jumper pins, which further suggests the PSU has some life in it.

For reference, it's sitting here with the following cables plugged in:

  • 24 pin ATX12V 2.x connector,
  • 4 pin P4 connector,
  • the CPU fan is attached to the CPUFAN1 header,
  • the case's power on switch is plugged in to the power on header of the front panel jumpers (the only connection to the case!), and
  • an HDMI cable to TV.

I don't think I've forgotten anything that should be needed for it to POST, and it's continuing refusal to do so is... troublesome. Any ideas?

gsnedders

Posted 2015-08-24T20:24:27.100

Reputation: 151

It sounds from the description like you're expecting the computer to turn itself on. If you've connected the power switch, you haven't said so. – David Schwartz – 2015-08-24T20:31:51.040

@DavidSchwartz um, uh, I mixed up words. It's connected to the power switch, and jumping the switch's jumper does equally little. – gsnedders – 2015-08-24T20:46:07.243

Without putting the PSU under load you can't properly test it. Seems to me you have had two complete set of components bar the PSU and both times not working. I would try another PSU. – albal – 2015-08-24T20:56:35.060

Answers

2

So I somehow managed to mix up the COM port headers with the front panel headers when prodding stuff with micrometer today, and the power button on the case seems to not work, bizarrely. Having the micrometer across the power switch jumper powers it on and it seems to work. Hurrah!

gsnedders

Posted 2015-08-24T20:24:27.100

Reputation: 151

It's likely because you connected the power switch to the power light connector. – David Schwartz – 2015-08-25T18:42:11.470

Nah, not least because jumping the two pins it was attached two causes it to start. The cable is fairly obviously broken—where the cable has a 90° bend in it within some insulating tape there's nothing within the tape, neither wire insulator nor wire. Given the number of times I took the motherboard out of the tiny case trying to see what was wrong before it went back as DoA, I likely just forced the wire back too far at some point and broke it at the weak point. – gsnedders – 2015-08-25T18:47:08.607

Asked: 2015-08-24T20:24:27.100

Viewed: 412 times

Active: 2015-08-25T00:32:40.843