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Fried Mobo after power flicker?

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by astrodude50

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Hi, a friend of mine has an HP 8756c which was running xp home until a few days ago. It was plugged into a surge protector and the power went off and came back on, but the computer would only show the blue HP Invent screen. The hdd light is staying on, and the keyboard light blinks repeatedly. I unplugged everything from mobo and took out cmos battery, still can't do anything with keyboard or access bios via F1. I took out memory and uplugged all from mobo and got beeps from the mobo, 8 total (1-3-3-1 sequence) The mobo is a Mercury MEW AM, and according to HP, it should have been running Mercury bios version 1.1, but I'm pretty sure I remember seeing Phoenix when messing with it while it worked a couple months back. HDD tested good, FDD won't come on, and both cd drives light up and open. I put in a pci video card thinking it may have knocked out onboard video, but that didn't change anything. Any ideas or is it time for the dumpster?

8 replies

by langlier

I'd test it and then even if it tests good try a known good PS. If replacing that doesnt change things then yes I'd say its time for a new board.

by astrodude50

Thanks for the reply...I pulled out the PS and used one off my spare which works without a glitch. Unfortunately for my friend, that's not going to fix it! It behaved exactly as it did before, still can't access the bios, and it won't post removing the memory or adding the video card in case the onboard was bad. Someone I spoke to mentioned maybe the processor, at this point, who knows? Unfortunately all I do is tinker with this stuff, so I don't have the tools to test it all.

by cg it

POST requires memory as it's one of the things the self test checks. No memory and the system will hault and give you beeps.

no keyboard present and the system will hault on you as default BIOS settings [well least earlier BIOSs] were hault on all errors.

the fact that it's beeping is a good sign, means at the least the processor is doing something [if it wasn't you wouldn't even get power on] You get power or there wouldn't be beeps.

the fact you see the HP screen is a good sign as well. Bad video you'd get a black screen and the monitor would tell you "no signal".

to bad the keyboard doesn't work TAB is the toggle between the splash screen and post screen. Try a different keyboard with just the processor and memory in it.

minimum you need to post is a processor, memory, keyboard and a monitor to see everything. if all those components are working, you'll get a missing boot device but ha ha you got to that point so you know it might be the hdd, hdd power, hdd data cable.....

by mjd420nova

If it's not the P/S then it would have to be the motherboard. The beep codes were correct if no memory is installed. Something on the MOBO failed and is not responding back to the CPU, causing the load sequence to halt.

by astrodude50

Thanks for the clarification on the correct responses on the beeps. In the previous tests that I was doing before, I only had 1 stick of memory, the processor and the keyboard hooked up. The keyboard kept blinking and it froze on the hp screen. I tried 2 other good keyboards, and none worked. The floppy drive also was not powering up, and it was set to boot before the hdd and the cd roms. Now when I plug in the keyboard and turn it on I don't even get the hp screen, it's just blank. I think the power flicker did it some injustice, but as I tried to explain to my friend that they were lucky it lived this long! Thanks for all your help...I may need some advice about replacing the mobo, as my friend doesn't want to get rid of it. I looked for a comparable one, but they're hard to find so old...any ideas where to look?

by astrodude50

I took a look at the processor on the mobo, and this is what it said...Intel PGA370. The mobo that is on this thing is a Mercury MEW Am - PIII 850mhz processor running 256 pc100 sdram. Definitely not up to par at all by today's standards. My friend is old school and just wants to replace if it can be done less expensively without having to replace all the other hardware. OS is not an issue, have retail XP already installed on hdd. Thanks again for helping a noob like me guys!

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