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Hello good people!

I have just build a htpc. The mohterboard is a ga-ma78gm-ud2h with an AMD X2 250 Processor, it has a 1G samsung harddisk, a Infrared USB receiver.

The PC seems to boot just fine when it has been unplugged from the mains. But when I shutdown the pc and want to restart it, it just doesn't start anymore. I have to unplug and replug it from the mains and after that it will start just fine.

Does anyone know where I should start looking?

Thanks a lot for you help!

Asimov

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  • Latest Post Latest Post by Bob_180_Bob

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A short, practical add-on to the thread: the symptom you describe — the build starts fine after a full AC disconnect but will not start after a normal shutdown unless you unplug and replug mains — most often points to a power-sequencing problem (the PSU’s standby rail or the motherboard’s power-control logic getting “stuck”), not a Windows-only issue. That pattern is a common sign that the +5VSB / Power-Good sequence isn’t happening reliably, so the board never sees a valid startup condition. (superuser.com)

Order these checks from least- to most-invasive:

  • Remove the IR USB receiver and any USB devices that draw power from standby, then shut down and try to restart. Bus-powered devices can load the 5VSB rail.
  • Try a minimal-boot: leave CPU, one RAM stick, integrated video (or GPU), and the motherboard only; disconnect extra drives and cards and retry.
  • Bypass the case switch by shorting the two front-panel power pins on the board briefly to confirm the switch/header isn’t at fault.
  • If comfortable with a multimeter, measure the 24‑pin connector: purple pin should read ~+5V (5VSB) with the PSU plugged in; the green (PS_ON) and gray (PWR_GOOD) lines show the on/off and OK sequencing during a start attempt. Missing/unstable 5VSB or PWR_GOOD points to the PSU or standby circuitry. (repairfaq.org)

Also check the GA-MA78GM-UD2H BIOS power options (AC Back / restore-on-AC-loss, power-on-by-USB/keyboard, wake events) and disable wake-from-USB/keyboard features while testing. Updating the board BIOS is reasonable only if Gigabyte’s notes mention power-sequence fixes. (gigabyte.com)

If the measurements or minimal-boot point at the PSU, a swap with a known-good PSU is the fastest, cheapest confirmation; many of these faults come from aging capacitors, sticky protection logic, or a failing 5VSB circuit and warrant PSU replacement. If a new PSU doesn’t cure it, the motherboard’s standby circuitry may be damaged and needs bench diagnosis or RMA. Note the exact LED/fan behaviour on failed attempts — that detail is useful to a repair shop. (hardforum.com)

(Added in context of ’s original report and ’s OS‑level suggestion: focus the next steps on power-stage diagnostics before doing more software-level troubleshooting.)

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Member Avatar for Asimov6

Hi,
Just a small point as I am a bad typist (as well?) but a 1g hard drive??

Yes, a typo, it is a 1000g harddisk

Member Avatar for Bob_180_Bob

No problems, did you try a SFC?

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