PC will not power up with USB devices

[Paul Phillips]

Please help,

My P4 titan motherboard with WD SATA will not power up with self powered usb devices plugged in (Memory stick, usb Hardrive, scanner etc)

There is no POST, no screen, no fan noise.  It is as though the PC is not plugged in. (it is though, I checked!)

Have tried changing power supply and a PCI usb hub.
unplugging the problem device will allow the system to boot and plugging the devices in after system boots is fine with none of them exceeding the 500ma power limit.

Any help will be appreciated

Thanks

[Raptor]

My computer can not boot up either with my external (FHD2-Pro) Hard Disk Drive connected.

I do not know if there is a work around. Have you tried disabeling booting from USB devices in the BIOS?

[merlin_2]

is this a self build.

[Paul Phillips]

It is a self build,

.....I do not know if there is a work around. Have you tried disabeling booting from USB devices in the BIOS?

It does not even get to P.O.S.T let alone read booting information in bios.  The motherboard does not get any power at all with USB devices plugged in

[Fed]

I know you said you changed the PSU but it sure sounds like a PSU problem.

"When the computer is powered on, the internal power supply initializes. The power supply doesn’t immediately provide power to the rest of the computer. First, it determines whether it can supply the proper voltages that the computer’s components require. The power supply sends out a POWER GOOD signal when it determines that it can supply reliable power to the rest of the computer. When the chipset receives this signal, it issues a SYSTEM RESET signal to the processor."

Do you have complete confidence in the size (watts) and quality of both PSUs?

[Paul Phillips]

Both PSU's work fine in other systems and are both 400w "True Power" supplies.

Am thinking about trying a remotely powerd USB1.1 hub
if I can find one cheap enough.

[Fed]

Can you unplug the usb devices then enter bios & have a prowl around in there for the usb setting options?

[Paul Phillips]

Everything looks normal in BIOS but how will this affect anything if power doesn't even get to the BIOS?

I have noticed that the problem gets even worse with PCI devices plugged in (PCI USB hub, PCI Network card etc)  System would not fire up until these were unplugged but only if I tried to fire up with the USB devices plugged in, could  be a problem with the PCI controler.