Test for bad Motherboard VS bad CPU

Question

I'm working on an HP Pavilion a6300f PC ( http://h10025.www1.hp.com/ewfrf/wc/product?lc=en&dlc=en&cc=us&product=3644689 ) that wont boot up. (no display, no beeps, no lights other than power, the cd drive, and for a split second the hd light when you first turn it on)

I'm told a few months ago with stock parts (nobody opened the case since it was purchased) it just wouldn't boot up. I tried using a different monitor, and a DVI connection instead of VGA.

When turned on, I hear the hard drive spinning up, but it never actually seems to do any read/write noises. It has integrated video, but I took out the pci modem that was on it, and tried using one stick at a time with both of the two RAM sticks at a time on it.

I've tried removing all unnecessary connectors (USB/etc) and reseating all connectors/jumpers I could get my hands on, as well as blowing dust off the motherboard.

I swapped the power supply with no luck (I don't have any other compatible parts to swap), though the current power supply connector leaves four open pins on the main motherboard connection. (weird?)

This all leads me to believe it's the CPU, but I suppose it could be the motherboard as well. Is there a way to tell without seeking replacement parts?

Solution

Pull all the RAM, if the system doesn't beep then the POST isn't happening and it's more than likely your motherboard.

I've worked on 100's of machines with similar no POST problems over the years (with everything but board, CPU and power supply left as installed suspects), and once it was the CPU, every other time it was either the power supply or motherboard. Since you've tried a new power supply and it didn't help, I'd bet money it's the MB.

As others' said in comments, determining for sure without having known-good parts to test with is nearly impossible.

HTH...

Comments

[rockit]

Determining whether it's a bad motherboard or a bad processor is usually difficult to accomplish without the use of known good parts. Regarding the power supply, try looking for another 4-pronged plug. The one in black & yellow is usually for the CPU. There should be another one to fill the 4 open pins on the motherboard connection.

[Jane Panda]

I don't see another four prong on the power supply - I'm hearing there were no hardware changes, would it boot with those pins empty?

[MDMarra]

The 4 extra pins on the main power connector is for the PCIe slot. If there's no PCIe video card in the machine you should be fine.

[Jane Panda]

Well there's another similar HP machine that is AMD drat (for swapping parts I mean), that doesn't beep when it boots even though it comes on fine... Still, I would have expected some complaining without RAM and it was quiet. I'll see about a mobo, see what I can come up with. Thanks for your all guys help!

[Jane Panda]

Turns out it was the motherboard - (trivial after-story) the chick didn't believe me (even though I got a $65 quote for a decent intel replacement board) and she took it to a shop... $285 later they said it was the mobo and replaced it. Good call techie007, you were dead on.