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I just got this computer (not from a store) and I noticed that the damn thing wouldn't turn on. so the first thing I thought was that the power supply was shorted I checked for the light on the back of the power supply to kick on when I plugged the cord into it didn't get a thing.

But later on I took out the power supply to try others but before I tried another i plugged it in normally without it hooked up to any components, the green light on the back seemed to turn on. The minute I noticed that I put the power supply back in the computer than I plugged the cord in than the green light kicked on thinking it might work this time.

The minute I hit the power button I was watching the light on the back of the power supply it kicked off so from there I'm either thinking its still a power supply problem or maybe everything else on board is either fried or its the mobo. I'm posting a link to the info on this computer for everyone else to make this more convenient for those needing to read up about it.

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Short summary and a practical path forward based on the symptoms you posted and ’s observation about the motherboard commanding the PSU: the fact the PSU LED lights when it’s out of the case but the LED (and the unit) drops the moment the system is asked to power up strongly points to the supply detecting a fault and shutting itself down (over‑current / short protection) rather than a simple front‑panel or LED problem. (tomshardware.com)

Steps to isolate the fault (do these in order; keep safety in mind):

  • Remove everything non‑essential (all drives, optical, discrete cards, front‑panel USB, extra fans). Leave motherboard + CPU (with cooler), one stick of RAM, and the PSU. Confirm the CPU 4/8‑pin power lead is seated. Try powering.
  • If it still cuts, disconnect the case power switch header from the board and briefly short the two power‑switch pins directly on the motherboard to rule out a shorted/stuck case switch.
  • Visually inspect the board (around VRMs and near the CPU socket) for bulging/leaking capacitors, scorch marks, or dislodged components — bad caps or PCB shorts can cause exactly this immediate shutoff behavior. (tomshardware.com)

If the problem still looks like the PSU: verify the PSU’s standby and rails (use a multimeter or an inexpensive PSU tester, or swap in a known‑good PSU). Check that 5VSB is present before trying to power the board, and test the main rails under a light load — a PSU that dies under small load needs replacing. Do not open the PSU; working inside it is dangerous. (lifewire.com)

One more note about OEM systems: some HP/Compaq machines use slightly different power/ID wiring and low‑wattage OEM supplies. Before swapping in a random ATX supply, confirm compatibility or use a tested OEM replacement—there are guides documenting HP proprietary pin schemes and safe adapter methods. If any step is uncomfortable, take the unit to a shop; mains voltages and PSU internals are hazardous. (instructables.com)

Member Avatar for 4th&3wood

The motherboard shorts out two wire in the harness from the PSU to turn the PSU on, so the PSU will not turn on without those to wire being shorted. You can use the following technique to determine if the PSU is working.

The purpose of this procedure is to bypass the motherboard to test the PSU.

Caution: This procedure will involve working with live 12VDC electrical potentials which if handled improperly may lead to electrical shock. Proper precautions should also be taken to prevent electrostatic discharges (ESDs) within the case of the computer. For safety purposes please follow the instructions step by step.

First, shutdown your computer. Then unplug the power cable going into your computer.

Once you have opened the case, touch the metal of the case to discharge any static electricity.

The connector of the PSU which connects to the motherboard is readily recognizable by the number of wires in the bundle. To disconnect it you will need to press on the plastic clip to disengage it and then pull the connector up and away from the motherboard. Please take notice of the location of the locking tab and the notch on the socket of the motherboard, this will only connect one way as it is keyed. This wire bundle will have a memory of the way it has been installed and will want to bend back that direction, you may have to play around with it to find a position that the connector will stay in the same position while you run the test.

http://i68.photobucket.com/albums/i35/carn3s/th_main24index.jpg[/img]

From the top left to right the pins are 13-24, the bottom from left to right are 1-12.


Please notice that there are PSUs with 24 pin and 20 pin connectors, the location of the green wire in the 24 pin connector is #16, and the green wire in the 20 pin connector is #14. If you look at the connector with socket side facing you and the clip on the top the number one pin will be on the bottom left corner. This makes the pin out for the 24 pin connector from left to right 13-24 on top, and 1-12 on the bottom. The pin out for the 20 pin connector from left to right is 11-20 on top , and 1-10 on the bottom. If you look at the connectors you notice that these are sockets that fit over the pins on the motherboard where the PSU cable attaches, this is where you will place the jumper. For a jumper you will need a piece of solid wire about the size of a paper clip (20-22 awg), preferably a wire with insulation. It will need to be large enough to fit firmly into the socket so that it will not need to be held in place while testing. You are at risk of electrical shock if you are holding the jumper when you power up the PSU. Insert one end of the jumper into the socket of the Green wire, and insert the other end into the socket of any Black wire.

Once the jumper is in place plug the cord back in. If the PSU is working properly the case fans, optical drives, hdds, and LEDs should power up and remain on. I would suggest that you not leave this connected any longer than is necessary for safety purposes.

To reconnect the 20/4 pin connector unplug the power cord, remove the jumper, and reconnect the connector. Take a moment at this time to make sure that nothing has been dislodged inside the case.

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