Member Avatar for ozPJ

Howdy,

Went to put some hot cross buns in the toaster..... tripped the safety switch. I reset the safety switch....

Went into the office and the PC was off (it had previously been turned on). Tried to turn it on, but would not start up. I assumed it was the power supply. However I noticed that the light was on where there ethernet cable was plugged into the machine. So power was getting to the MB.

Opened the machine up and had a look to see if I could find anything obviously wrong. Plugged the power cable back in, and tried to turn it on again - no go. Unplugged the power cable, and then plugged it back in. Power supply fired up, as did the fans on the MB and CPU.

Put side back on case, and then plugged all peripherals back in. Repeated same turn on procedure. Nothing comes up on screen, no noises like normal boot up etc.... I.e. no bios check, ram check etc...

So not sure if it is power supply, motherboard, hdd, graphics card.

Any thoughts?

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  • Latest Post Latest Post by Chaky

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Useful follow-up steps based on the details posted (the LAN jack LED while the PC otherwise won’t POST is an important clue). That LED usually means the ATX standby rail (5VSB) is present, so the board is getting standby power even if the main rails or the power-good signal aren’t coming up. Fans that spin when you reseat the mains can be a transient response; they don’t prove the motherboard and main rails are healthy.

Try this focused, safe diagnostic sequence:

  1. Power off and unplug. Visually inspect the motherboard and PSU for bulging/leaking capacitors, burn marks, or a smell of burned components.
  2. Clear CMOS (remove the battery for a few minutes or use the clear jumper/button) to rule out a corrupted BIOS setting.
  3. Bench the board: remove the case from around it, leave only CPU+heatsink, one known-good RAM stick in the recommended slot, the 24-pin and CPU 4/8-pin power connectors, and the system speaker (or attach a small speaker to the header). Do not connect HDDs, optical drives, USB devices, or PCI cards. Try powering the board by shorting the two front-panel power pins briefly (use an insulated screwdriver) to eliminate a faulty case switch.
  4. If that still gives no POST and no speaker output, try a different, known-good PSU before doing any intrusive testing. If you have a multimeter and are experienced, verify the main rails (+3.3V, +5V, +12V) and the PSU “power-good” signal (grey wire) — otherwise leave PSU diagnostics to a shop.

If none of the above produces POST codes or diagnostic LEDs, the probable next steps are swapping the motherboard or CPU (or having a shop bench-test with spare parts). Follow anti-static precautions and don’t open the PSU (high-voltage caps). This narrows things faster than replacing drives or peripherals; it follows ’s stepwise approach and the caution noted about fan noise not guaranteeing component health.

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Member Avatar for belikemike

Start with as little plugged in as possible.
Try one peripheral at a time. Your damage could be one of many things, so you must use process of elimination. Be patient.

Member Avatar for Chaky

My money is on the PSU. Spinning fans doesn't mean that the PSU is working properly.

Second guess would be VGA. Fried VGA would cause some beeps too. (1 long 7 shorts)

Third guess is RAM.

(etc.)

As Mike said, process of elimination is the ONLY way to single-out the cause.

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