Here is a weird one.
HP Pavillion a600n
Power on and lights come on, fan spins, drives spin up
USB or PS/2 keyboard never comes on and machine does not POST
Move jumper to reset CMOS has no effect.
Pull plug and remove CMOS battery, wait 30 seconds
Plugin and boot with or without battery
Will boot into Vista IF I DO NOT ENTER BIOS SETUP AND LET IT SKIP OVER THAT
Once I shutdown, it will not boot again until I remove power and CMOS battery
If I change BIOS settings or go into BIOS setup at all, it will not boot after exiting BIOS settings
It sees all components properly in BIOS setup and lets me make changes but once I exit BIOS setup it does not POST again until I hard reset.
Things I've tried.
Replaced battery (verified with voltmeter both old and new were 3v)
Removed all components, unplugged everything from the motherboard, hooked it up to a different PSU
Same behavior. Fans spin but no POST or beeps (even tried with fans disconnected and no CPU or RAM just raw mobo)
I remove power and CMOS battery and it starts, shows POST errors and beeps like it should.
MemTest passed but it doesn't matter if there is memory plugged in or not.
The chip that stores the BIOS code is bad. When it is forced to load the default copy it works but once that copy is loaded into CMOS memory it is corrupted. Mobo must be replaced.
Later I'm going to attempt a BIOS flash. It hasn't been done yet because the only way you can flash it is via the Windows OS (Vista in this case) and I do not trust flashing it that way so I'm trying everything else first. If there is a problem with the chip, flashing from the OS only can easily have a problem that will make it nearly impossible to fix.
Anyone else see this before?
EDIT: It is an HP OEM motherboard, that is why the only way to flash it is via Vista program or hooking up to the SPI header (not going down that road )
Edited by James Litten, 15 March 2013 - 10:14 AM.