PC ON/OFF Switch Mode?

[excitron]

An old Win XP station I have, that I preserve for various processes, decided not to go on one day. I suspected the power supply had died, so I replaced it and the system was still dead. This got me to wondering if it's the on/off switch. Although it "clicks" on/off, I'm under the impression this is a momentary-on switch, no? If so I feel perhaps it's failed, even tho it still "clicks".

Of course, the MB may have dropped dead for some reason, or some other component I'm not thinking of may be at fault, but it would strike me odd, as the system was running fine when I shut it down.

So, A) Is the PC on/off switch momentary on, and B) could it be something else, and if so, what? If it's momentary on, would the reboot switch substitute as a temp to test it out? I may just decide to buy a new case anyway, but it just got me thinking.

Thanks for any info on this.

Edit: OOPS, sorry, for got to mention hardware.
MSI MS-7309 MB
AMD Athlon(tm) 64 X2 Dual Core Processor 4000+
DDR2, PC2-5300 (333 MHz), 1024 MBytes x 2
Crucial 525GB MX300 SATA III system drive
Hitachi HDP725050GLA
nVidia GeForce 210

The case itself is an old full size generic unit from the early 2000s that I probably picked up at CompUSA, big and heavy.

 

[R_1]

a) yes this is a momentary switch, a normally open momentary switch. you can test the switch by unplugging it from motherboard and connecting the pins it connects to with a conductor, close the circuit and the PC should switch on. if this happens the switch may be bad, either the switch or the wires on the switch.
if your case has a reset switch you can swap it with the power switch and use the reset as the power switch.
b) a short in the wires the switch is using, bad motherboard, faulty ram, faulty CPU could be many things keeping the system from posting

 

[excitron]

Thanks, I'll check it out.

 

[Paperdoc]

I expect that is all correct. Just a note that the answer depends to some extent on how "old" that machine is. The current design (in use for a couple decades) has a momentary-on pushbutton switch on the front panel, and it has two small wire leads to a pair of pins on the mobo Front Panel header, usually at bottom front corner of the mobo. The front panel "reset" pushbutton is the SAME type of switch and likewise connect to two other pins on that same header.

Prior to that, though, up to mid-to-late 1990's, power supply designs and their connections to the mobo were different. In those designs there were a set of heavier wires coming out of the PSU going directly to the front panel power switch. On an old machine I had the switch was a rocker type, but it could have been a latching pushbutton. That switch was NOT a momentary-on type. But NOTE that it was wired directly to the PSU with heavier wires, and NOT to a mobo header with only two light wires.

 

[excitron]

Well, I tried to short it at the MB, and got nothing. I checked the switch with a VOM, and the switch is fine.

So I have to assume the MB just died for some bizarre reason. There's just zero response from the system, like it's not even plugged into the wall.

 

[Paperdoc]

I agree. You are confident the PSU is good, but still you get zero response from anything on the mobo. I assume the power switch on the back of the PSU is turned on. Even a mobo with a dead CMOS battery will still turn on if the mobo is OK.

 

[excitron]

I agree. You are confident the PSU is good, but still you get zero response from anything on the mobo. I assume the power switch on the back of the PSU is turned on. Even a mobo with a dead CMOS battery will still turn on if the mobo is OK.

I'll try a third PS just to make absolutely sure. I dunno WTH else it could be except the MB. Strange that it just died overnight like that, was working perfectly.

 

[Paperdoc]

Check that the CPU cooling fan is plugged unto the CPU_FAN header securely. Some mobos will refuse to start up if they sense no fan there that actually turns when it starts to boot.