Boot Failure - not even a BIOS beep

[Kleffman]

Hi all,

Yesterday I got home and suddenly my computer wouldn't turn on. It'll make a silly attempt but then kill the power before it even gets to the BIOS beep. All that happens is fans start spinning up, lights turn on etc, and that only lasts about one second before it powers back off. My first step was to blow all the dust out of it and then suddenly it booted. That turned out to be random luck because this morning it's got the same problem back. I suspect the PSU is faulty. I have unplugged all drives and right now the only power connectors are to the motherboard (bare minimum). I even ruled out a bad front case switch by manually shorting the two pins on the mobo.

Anyone agree it's probably the PSU or does this sound like the motherboard went bad (god I hope not).

 

[wahnula]

Look for bulging or leaky capacitors:

http://www.badcaps.net

on the mainboard. PSU's are cheap, go with a name-brand unit, worst case you have a spare for the future.

It may not be just chance that after you cleaned it it booted; thoroughly disassemble and clean the whole rig, it may be a dust bunny shorting out traces behind the mainboard. This will also give you an opportunity to examine the components up-close.

Tony

Users helping Users...

 

[ski]

Make sure that the CPU's fan runs when the system is started. If it does not, then a CPU fan failure option in BIOS may be shutting down the system to prevent the CPU from overheating, and getting damaged.
If the fan runs and it has a 3-wire MB connector, then check that the connector is making contact with all 3 prongs on the MB's terminal.
If that's ok, then either the fan's speed sensor wire(normally yellow), or the fan's internal speed signal mechanism may be bad. To check this, reset CMOS either with a MB jumper(see your MB's documents), or by removing the CMOS battery for at least 30 minutes. This should reset the BIOS "CPU Fan Failure" option to its default Disabled setting. If the system runs ok after doing that, then replace the CPU fan, and re-enable the "CPU Fan Failure" option. If the problem happens again, then the MB's fan speed circuit may be bad.
If disabling the "CPU Fan Failure" option does not work, then make sure the CPU's fan and heatsink are completely dust free, the CPU's heatsink is securely mounted, and the thermal compound has not oozed out.
If that does not help, then either swap out the PS, or test it as shown here:

http://www.ochardware.com/articles/psuvolt/psuvolt2.html

 

[Kleffman]

Just an update...

Since it seems the easiest I went and got a new power supply. Same wattage (550 should be enough) Antec. Seems like that was the issue because now it'll boot up again. Also blew the dust out of it even more thorougly after that before reconnecting all devices. Hopefully that's the end of it.

Also I tested the PSU voltages as shown in the above link and they're all showing full voltage so I don't know what the problem was. I guess it only had an issue under load?

As always, thanks for the fast responses and help!

 

[G0AOZ]

Glad you got it sorted! Yes, PSU's often show correct voltages when not under load. Also, it is difficult to determine how pure the DC output is with a conventional test or multimeter. This is where an oscilloscope comes into its own...

ROGER - G0AOZ.