Member Avatar for paRick

I assembled a PC from scratch about 3 year ago. It has worked well for all these years other than a slight heat problem that I solved by adding an extra fan. I used a ASUS P4P800 SSE mobo P4 CPU, nvida FX5200, 2GB ram. All of a suden it went dead other than the fans, a green light on the bottom of the mobo and the blue power switch light. The poer switch does not turn it of, just the cut off in the back. My wife uses the rig and she rarely turned it off, it did freeze occasionaly. I tried disconnecting most of the ram, hard drive, video card and then powering up nothing. I was thinking it was the PSU because she had it running for "3 years straight" ;)then I was think the CPU may have finally expired form the old heat issue.
Hate to buy both or maybe a new mobo. any suggestions.

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Short summary tied to the thread: described a machine that powers fans and LEDs but will not respond properly to the front-panel switch and now fails to POST. and correctly pointed at power and memory as suspects. Below are additional, practical checks that were not covered yet and that help avoid buying parts blindly.

  • Bypass the case switch: unplug the front-panel power lead from the motherboard and momentarily short the two power pins on the header with an insulated screwdriver. This verifies the board itself can be told to start/stop without relying on the case wiring or switch.
  • Check the CPU power feed: confirm the 4/8-pin CPU power connector (next to the socket) is present and firmly latched. A motherboard can show lights and fans while the CPU power rail is missing or intermittent.
  • Physical inspection for old-age failures: look for bulging or leaking electrolytic capacitors and heat-damaged VRM components around the CPU area. Any visible damage makes the motherboard the prime suspect.
  • Bench test to rule out case shorts: remove the board from the case and power it on over a non-conductive surface (cardboard/plastic) using only CPU, cooler, one stick of RAM and power. This rules out misplaced standoffs, screws, or case contact.
  • Clear CMOS and speaker diagnostics: remove the CMOS battery or use the clear-jumper to reset BIOS settings, and attach a small PC speaker to the speaker header to capture beep codes (refer to the ASUS manual for codes).

If a multimeter or inexpensive PSU-tester is available, measure the main rails at the ATX connector while powered; this gives more reliable info than looking at a fan. Take proper ESD and mains-safety precautions. If none of the above isolates the fault, swapping in a known-good PSU (as suggested by ) or having a local shop bench-test parts is the next cost-effective move before replacing motherboard/CPU.

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Member Avatar for Bob_180_Bob

Hi,
It could be one of many things but I would try a new power supply first, it is the cheapest and can be used if you decide later to upgrade. Even though the fans and lights are working, the PSU could still be faulty. You have to decide if you will pay a tech to find the problem or start buying the parts it could be faulty and hope you find the right part early. You have tried most of what would be suggested here. Can you try a power supply from a friends PC?
PS. Many machines are run for well over three years straight with no problem, others burn out before 1 day of running.

Member Avatar for techsheaven

Do I understand that the PSU fan is turning? Sometimes certain voltages will fail without others. Most PSU fans run at 12v. You could plug in a usb device (one with lights) to check the 5v.

Another idea is to clean out the dust. Be sure to avoid electro-static discharge.

To check the RAM, you have already removed some of the RAM, now pull the other stick(s) and some that you pulled the first time.

Good Luck

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