Member Avatar for analogdog

I am trying to diagnose a problem with my ASUS A7N8X machine. It has 512 Mb RAM, an AMD XP 2100+ chip, and a Chaintech GForce 4 MX 440 video card in it. The machine runs Debian Linux 3.1r1.

I rarely shut this machine off, as it runs a BOINC client processing both SETI and climateprediction.net files.

Recently, I was having problems with the machine freezing after 1-10 minutes of running. All of a sudden, dead. System logs did not show anything funny, other than the reboot that always followed.

Then one night, I tried to shut it down, and it got into a cycle of reboots, never showing the BIOS. I guessed these were the power supply not sending "power good" messages to the mobo, and being forced to cycle to attempt to get to a "power good" message.

So I bought a new PS, 450 watts and installed it this afternoon.

Interesting: if the rear switch is on, the mobo sports a bright green led showing there is power to it. Press the power on button, and nothing happens. Literally, not even a minor humm, whir or blat.

I hopped on the werb and went through flow chart on hardware problems, and got to a bad switch. Tried swapping it with the reset button, but no dice.

Could the BIOS battery be dead? Could it be something else entirely? Maybe the mobo is dead?

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  • Latest Post Latest Post by djrivera1

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A short, targeted summary for and the thread: the bright green rear LED shows the PSU standby rail (5VSB) is present, while the complete lack of any spin, hum or POST when the power button is pressed means the board never starts the main rails. That narrows the fault to either the board failing to assert the PS_ON signal, a board-level protection/short that immediately kills startup, or a very uncommon PSU fault that only appears under motherboard control. Since a replacement PSU did not change behavior, the motherboard is now the prime suspect.

Useful diagnostic sequence (ordered to isolate quickly and safely):

  • Verify the PSU by starting it off-board (paperclip method) and measuring the +12V, +5V and +3.3V rails with a multimeter or PSU-tester. If the PSU delivers correct voltages, the supply is likely OK.
  • With the PSU connected to the board, observe the PS_ON (green) line at the 20/24-pin connector while the front-panel button is pressed. If PS_ON stays high, the motherboard is not telling the PSU to start.
  • If PS_ON is being pulled low but the system still dies, the board is likely tripping protection due to a short or failed power circuitry.
  • Move the board out of the case onto a non-conductive surface and try a bare-minimum bench power-up (single RAM stick, CPU, PSU, speaker) to rule out a short to standoffs.

Visual and component checks that often reveal the fault: inspect all electrolytic capacitors (especially around the CPU VRM and northbridge) for bulging or leakage, look for scorched MOSFETs or blown SMD fuses (often labeled F1, etc.), and check for cracked solder joints. These boards are old; recap or component-level repair can work but requires tools/skills. This advice expands on , and : the next sensible step after PSU verification is a focused board inspection and bench test. If PS_ON is never asserted and no obvious component damage is visible, replacement or professional bench diagnosis is the pragmatic choice.

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Member Avatar for Chaky

Did you plug in all the power cables? Are you sure about that switch? Try shorting the 2 pins the switch is plugged on. The CMOS battery should be ok, regarding it's age.

Member Avatar for caperjack

try removing all addin cards like sound ,modem nic ,ect ect ,also the ram process of emilitation

Member Avatar for djrivera1

Sound like the motherboard when then again knowing it a athlon xp could be the processor have die for no apparent reason. removed the cpu look for any dark spots on it if there is and it retail version RMA it. but if not go to a local store and pick up a new motherboard or ordered it if it work it was your motherboard if not it the cpu you can always return the mother if it doesn't work cpu you can't.

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