Computer Hardware Help → [motherboard] Interchanging CPU's to help isolate problem

I have a system with an ITX motherboard (let's call it Board A) which uses an Intel Celeron M 440 CPU; it works perfectly.

There is another system (with a different ITX motherboard [let's use the label Board B]); it has an Intel T9400 mobile CPU. I turned this on the other day; it worked for a few minutes, then the front-panel Power light went off and the system has never worked again. The power supply seems to be OK and I have substituted another power supply- still dead. So, the problem appears to be the CPU and/or the motherboard.

The T9400 will physically not fit (one extra pin) into Board A, so I cannot test this CPU. The Celeron M 440 will, however, fit into Board B.

Will the M 440 work in Board B (even if it is only for a few minutes), so that I can determine whether the motherboard itself is OK? I need to know if the motherboard or the CPU has failed, so that I know what replacement parts I need to search for.

Because the motherboard has been customized by the system maker, I hope that it is OK; a replacement CPU should be much easier to find.

Thanks in advance for any info that you can provide.

The Celeron uses Socket M, whereas the T9400 uses Socket P. From what I can tell, they are not compatible with each other. CPUs for either socket are readily available for cheap.

I was afraid of that.

Since I don't use PayPal, I can't look for a CPU on eBay; hopefully there is some other place where I can find one for a low price.

Sure wish there was a way to isolate the problem to the CPU or motherboard without substituting another chip, but I cannot think of anything right now. All I know is that there is no power being applied to the motherboard, since the board is not telling the power supply to turn on. When the system turned off the other day, it was stone-cold (since it had only been on for a few minutes), so overheating would not have caused the failure.

The BIOS is configured to automatically turn on the the system when AC power is applied; I have also tried actuating the Power switch- still no power. Connecting a power supply tester (which triggers the enable signal) indicates that the supply is capable of delivering all of the required output voltages.

I've never seen a CPU fail unless it was seriously overclocked and over-volted. It's much more likely that the motherboard has a problem. A shorted cap can prevent the power supply from coming up. The supply will detect an over-current condition and instantly turn itself off to prevent damage. You may see an led on the MB start to turn on or a cooling fan twitch just before the power supply kicks back off.

As a seller on ebay myself, I have no problem accepting other forms of payment as it cuts down on fees. I'm sure many other sellers feel the same way. You do not need a paypal account to buy things on ebay. Sellers must accept it, but they are also free to accept any form of payment the buyer wants to use. The thing is sellers aren't allowed to solicit different payment options, but if the request is made by the buyer this is no issue at all. Find what you need and ask a few sellers if they accept your form of payment. I used to love getting cash / money orders, but ebay has brainwashed buyers into thinking it's paypal only. These days I only get a few offers a year...

The system normally does not use a fan (it relies on a very thick aluminum case and an elaborate heat-pipe system to keep it cool), but there are (unused) fan connectors on the motherboard. I plugged a fan into one of the connectors and turned the system on- there wasn't a trace of movement of the fan blades. So, it appears that the power supply is not being turned on at all.

Thanks for the info regarding eBay. I looked there to see if I could find a replacement motherboard- nothing today; perhaps in the future.

I also called the manufacturer of the system to see if they might have a motherboard (even a used one) sitting around- there is nothing available. So, it appears that I am at a dead end (at least for the present).

There are perhaps other motherboards with the same dimensions, but they would probably not be compatible with the heat-pipe system that the system manufacturer designed (since this relies on the CPU, North Bridge and South Bridge chips being in specific locations). I wouldn't even begin to know how to locate heat-pipes with other lengths in order to come up with a cooling system for a motherboard which has a different chip placement.

Update- I used a paper clip to short the power-enable (Green) wire of the power supply to ground- a fan connected to the motherboard started spinning. Since there was no CPU heatsink attached, I only left the power on for a second, but this is a positive development.

Now, I can put the system back together (with a shorting jumper soldered in place) and see if the BIOS setup screens will display on a monitor. This may give me some clues as to where the problem is. It would be nice to be able to work on it without putting it all back together, but the case top cover is an integral part of the cooling system, so complete assembly is essential.