Long story short: we had a power failure, and my wife’s system does not power up.
System: Store bought, HP Pavilion 9400f, AMD Phenom X4 9750, 8GB RAM, 750GB HD.
When power switch is pressed, absolutely nothing happens, no fans try to spin, no lights appear anywhere, nothing.
HP docs on this system are not good.
I pulled the covers and looked around. I see no obvious burns or signs of damage.
Motherboard appears to be a MCP61PM-HM, HP P/N 5189-4598. I think this is an Asus based mobo. It has a pretty standard and obvious layout.
PSU part number is HP 5188-2589. It is 350W, but there is not a lot of hardware to drive in this system. And has worked unchanged for about 2-3 years.
Further diagnostics: the PSU has an LED, which does show green when external power is applied. This seems suspicious to me. So I ….
pulled the PSU, and ran standard bench tests. They are clean: 3.3 where expected, 5 where expected ,……
I should mention: this mobo does not appear to have a single ‘power present’ LED. Either that or I am blind.
I am looking for suggestions as to what to try next, because I am baffled at this point. I have the feeling that throwing a new PSU at this is not going to fix anything.
Would appreciate any thoughts from folks more savvy about hardware than I am.
Thanks, Guy
Forget capacitors changing if power is removed. Your computer has something called a power controller. Most do not even know it exists. One safety feature is a lockout. To reset the lockout in a controller, disconnect a power cord for a few seconds.
Never disconnect anything before making a measures (as another has noted). One minute with the meter could have answers a long list of unknowns. Start by measuring the purple wire (from power supply to motherboard) before powering the machine. It should measure about 5 VDC. But post the three digit number hear. Every digit contains useful information.
Do same with the green and gray wires both before and as the power switch is pressed. Those numbers will also result in facts that contain no speculation.
And finally measure any one red, orange, and yellow wire both before and as the power switch is pressed. Also report that behavior – in numbers.
What follows is a list of parts that are no longer only suspected good or bad. Listed will be ‘definitive’ answers – no more ‘it could be …’. How a computer really works (and it is simple) will also be learned.
Never disconnect or remove anything until hard facts (especially those above numbers) are first learned.