Member Avatar for fvdave30

Would a failing power supply start up the computer after all power was drained including removing of the CMOS battery. But, just shutting off the computer waiting and then turning on the computer cause the computer not to start up and give the impression that the video chip on the motherboard was not working?

Thanks,

Everett

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Short answer: yes — a marginal power supply can behave like this. Removing the CMOS battery and leaving the machine unplugged fully discharges the system so the PSU starts from a cold state; a weak PSU or one with failing electrolytic capacitors, a bad power-good signal, or temperature-dependent faults can pass a cold start but fail on a quick restart. That failure can look like “no POST/no video” even when the video subsystem is fine, because the motherboard never sees stable voltages.

Quick, safe diagnostics to narrow it down:

  • Visually inspect the PSU and motherboard for bulging or leaking capacitors and for any burn/melt signs.
  • With the mains switched on (but PSU disconnected from the motherboard if you prefer safety), check the 5 V standby rail (5VSB) on the 24‑pin connector with a multimeter. If 5VSB is absent, the PSU’s standby circuitry is failing.
  • If comfortable and cautious, use an insulated jumper on the 24‑pin (green PS_ON to any black ground) to force the PSU to run outside the case and then measure the +3.3V, +5V, and +12V rails under load. Watch the gray “power good” lead: it should go high a few hundred ms after rails stabilize.
  • If you get no spin-up or unstable voltages, stop testing — do not open the PSU (dangerous capacitors). Use a commercial PSU tester or have a shop bench-test it.
  • If the PSU supplies stable rails and a valid power-good, then investigate motherboard POST LEDs/beep codes, speaker header, or peripheral shorts. Also rule out a stuck/failed front-panel power switch by briefly shorting the two power pins on the board.

These checks will confirm whether the PSU is the culprit without repeating component swaps. For step‑by‑step bench procedures see and for ATX signaling details see ATX (Wikipedia). As suspected, intermittent start behavior often points to power-delivery problems rather than an immediate GPU failure.

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Member Avatar for dickersonka

If the computer wouldn't turn on, most likely the video card isn't bad. When a power supply is going awry, sometimes it may turn on the computer, sometimes not. Make sure all cards/ram are firmly in place, possibly remove and reseat them. If you still have the same result, trying replacing the power supply with a backup one if you have one.

Member Avatar for dickersonka

You also might want to check out the cpu temp, if it gets too hot it will shut the comp down and if it is too hot, the comp won't turn on.

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