Member Avatar for SuperSi

Recently I've tried to boot using rescue floppies and after POST the screen would flicker. I opened the case to check for loose connections. I found no loose connections but a whole lot of dust & lint on the CPU heat sink.
I removed and cleaned the heat sink and fan. Also one of my CD ROM drives had died a while back so I took the opportunity to remove it.
When I switched the P.C back on it would come to life and after about 10 seconds shut down again. Any ideas how to fix this?

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Dani AI

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Early, automatic shutdowns within seconds (especially before POST, as reported) are a sign the platform is protecting itself or losing power. was right to think about temperature, but the cause can also be PSU faults, motherboard shorts, bad front-panel wiring, or failing RAM. The quickest way to find the culprit is a small, ordered isolation procedure.

  • Power basics first: verify the 24-pin ATX and the 4/8-pin CPU power lead are fully seated. If comfortable, use a PSU tester or multimeter to confirm 12V/5V/3.3V rails are within tolerance; otherwise swap in a known-good PSU.
  • Minimal boot (breadboard): remove all drives and cards, leave only CPU, one stick of RAM, and video (or onboard). Try to POST outside the case on non-conductive surface to rule out a short from standoffs or stray screws.
  • Front-panel and switch checks: unplug the case power/reset connectors and short the two power pins briefly with a screwdriver to rule out a faulty switch or wiring short.
  • Memory and slots: try each RAM stick in each slot one at a time. A single bad module or slot often halts POST quickly.
  • Motherboard inspection: look for bulging or leaking capacitors, burn marks, or damaged traces. Any visible damage usually means board replacement.
  • Beep/LED diagnostics: attach a system speaker or watch onboard debug LEDs / POST code display if available. They give quick clues to the failing subsystem.
  • CMOS and BIOS: reset the CMOS with the jumper or remove the battery for a minute. A corrupted setting can sometimes halt early.
  • Safety: avoid powering repeatedly if the system smells hot or components get very hot. If unsure about working inside the PSU, get professional help.

Preventive notes: keep heatsinks and fans clean, ensure secure cooler mounting and firm power connections, and periodically check cables for frays. These steps will help localize the fault faster and avoid unnecessary parts changes.

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Member Avatar for Thong_Ispector

Sounds like a heat problem. Can you stop the POST and get into the Bios/CMOS Setup and check the temp?
Did you verify the cpu fan is running? Did you change where it plugged in?
Did you wiggle or move the heat sink much? You may need to pull it and re-apply heat compound.

Member Avatar for SuperSi

Sounds like a heat problem. Can you stop the POST and get into the Bios/CMOS Setup and check the temp?
Did you verify the cpu fan is running? Did you change where it plugged in?
Did you wiggle or move the heat sink much? You may need to pull it and re-apply heat compound.

Did wiggle heat sink a bit when cleaning. Fan is working. The machine stops before POST even comes up.

Member Avatar for SuperSi

ALWAYS CHECK THE BASIC STUFF FIRST!
I finally got my P.C working again after securing the heat-sink properly.
If the clamps are not applied correctly the CPU will shut down to protect against overheating. Anyway I still had a blank monitor. When I was reattaching the moniter cable I noticed it was frayed. Only when I wiggled the cable a bit did my monitor work again.
So everything is all fixed now. :D

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