Wwhats the h/w issue?

Some PS have Glue on some components to help keep them in place and this should be there.

As for Power Supplies they have 3 Distinct Voltages these are 12 V DC, 5 V DC and 3 V DC and they need sufficient current for each Voltage Rail. All a LED illuminating is saying is that there is 3 V DC present and in no way implies that there is sufficient current on that 3 V Rail. It in no way implies that the 5 or 12 V DC Rails have any Voltage or Current.

I would first test with a [b]Known Good[/b] Power Supply and if that cures the problem the PS was shot. Of course it may do absolutely nothing at all or even destroy the Known Good Power Supply if there is a Massive Short Circuit on the M'Board.

Recently I had a Customer buy a New M'Board, CPU, RAM, Optical Drive and HDD in an attempt to save himself some money by not bringing it to me and none of that made any difference. He wrongly implied that because the Fans Ran the PS was OK but when I replaced the PS the New Computer worked perfectly as it did when I replaced all of the Old Components.

I then pointed out he had a Warranty for a reason and it wasn't necessary to buy replacement parts to fix a system under Warranty. Still at the end of that after he bought a new case he had 2 working computers. ;)

Col

And remove all of the crud from behind the switch. You should also check for badly molded plastic Parts in the guise of the actual push button which could be jammed in the front cover of the case.

As the On Switch is just a Momentary Contact Switch you can use the reset switch to test the unit with as the Power On Switch. ;)

Col

Well,

It could be the CPU or the RAM.

Just as likely that a bad PSU damaged the original and the new motherboard.

However, it would not hurt to check and make sure that the clear CMOS jumper is not set on the new motherboard. If the clear CMOS jumper is set, you get the same symptom as a dead system.

That green light on the motherboard only verifies that the 5 volt standby voltage is present. No validation that anything actually works, or that the power supply is properly regulating the critical voltages.

I use a cheap ($30 US) ATX power supply tester to test both suspect and new power supplies.

Chas