Member Avatar for natural

Hi All

Major problem here. Just wantt to know if anyone has any idea what this might be.

The computer was asleep at the time the power went off. Now, if I hit the stratup button, the light comes on as I hold the button down, but that's it, not boot up, nothing.

Is this a problem with the power supply? Has something been fried?

Any help much appreciated.

  • 2 Contributors
  • 2 Replies
  • 86 Views
  • 23 Hours Discussion Span
  • Latest Post Latest Post by natural

Dani AI

Generated

The symptoms described — machine asleep during a blackout, power LED on when the button is held but no boot — point to two common causes: a PSU failure from a surge, or the Power Management logic getting stuck. is correct that surges often damage the supply, but ’s followup shows a PMU-state reset can restore a G4 without replacing parts. That means the immediate failure was a hung power-management state rather than catastrophic hardware damage in this case.

Quick diagnostic checklist to apply before buying parts or calling a shop:

  • Observe behavior on power-on: do fans or drives spin? Any smells, heat, or visible scorch marks? No movement usually implicates the PSU; fans/spinning with no boot suggests PMU/logic.
  • Do a careful visual inspection (power unplugged): look for bulging or leaking capacitors on the PSU and logic board, and for blown fuses or scorch marks.
  • If comfortable with basic electronics, confirm DC rails at the board connector with a multimeter or try a known-good compatible PSU; if not comfortable, stop and get professional help.
  • Do not probe the PSU while it is connected to mains; capacitors can store lethal charge.

Next steps and prevention: if the Mac now boots, run it under normal load and watch for instability (restarts, missing rails, random shutdowns). If anything smells burnt or behavior recurs, replace the PSU and keep the machine behind a surge protector or UPS. When replacing parts, match the exact G4 model and PSU part number — G4 PSUs are not universal.

Recommended Answers

All 2 Replies

Member Avatar for John A

Ugh. There was probably a huge powersurge before the outage, which probably fried your power supply unit in your G4.

The good news is is that the PSU generally sacrifices itself for the other computer parts, so generally a power surge will not harm other computer parts.

As for fixing I'm sorry, I don't really know much about G4's PSUs. Consider asking at your local Apple store for power supply units and additional information, or if you're not feeling up to it, get them to do the repair for you.

Member Avatar for natural

Ugh. There was probably a huge powersurge before the outage, which probably fried your power supply unit in your G4.

The good news is is that the PSU generally sacrifices itself for the other computer parts, so generally a power surge will not harm other computer parts.

As for fixing I'm sorry, I don't really know much about G4's PSUs. Consider asking at your local Apple store for power supply units and additional information, or if you're not feeling up to it, get them to do the repair for you.

Thanks for your reply but I found the answer.

I just reset the PMU button on the motherboard and it booted. See this page on Apple's website:

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.