Dell XPS 8300 won't boot even after replacing motherboard and power supply

[hokeypokie]

Hi, I have a Dell XPS 8300 that will not power up. When plugged in, the power supply shows green LED and the motherboard shows orange LED. Nothing happens when the power button is pressed. I switched out the power supply and the motherboard and still have the same problem.

But here's what make this tricky.

- I connected the motherboard to just the 2 power cables from the power supply, CPU, heat sink fan, and case fan, case power switch. It turned on (fans on) when pressing the switch. There were beeps indicating missing memory.

- The next time I tried, same problem came back. Pressing power switch didn't do anything.

- I disconnected the case power switch (power cable unplugged) and short the switch pin on the motherboard while plugging in - nothing happens.

- I unplugged the power cord. Case switch still unplugged, switch pin on motherboard left alone. When I plugged in the system, it turned on right away (very weird) - fans running and I got the beeps.

- I unplugged and connected the case switch, plugged it back in and the PC turned on without pressing the power button.

- I added 1 memory to slot 1, then plugged the PC in. It turned on without pressing power button no beep.

- I unplugged the power cord, plugged in the monitor and then the power cord, and now it doesn't turn on. I unplugged the monitor and still doesn't turn on.

So the system is back to where it was. Can't get it to turn on anymore now. Any help would greatly be appreciated. Thank you!

 

[Dark Lord of Tech]

Try unplugging the power cable from the computer tower and then unplug all the peripherals such as keyboard, mouse etc. After unplugging all the peripherals, press and hold the power button in the front of the tower for 15 to 20 seconds.

 

[hokeypokie]

Tried that and still no response from the power switch.