Processor Overheating

Hi everybody. Hopefully this is in the right place for this; it's hardware related, and I didn't see a place for help questions.

I have an old Toshiba A25, and lately the processor has been overheating and shutting down within 30 seconds of turning the machine on. I took it apart, and everything was visibly okay. I also added some new thermal compound to the processor and graphics chip, and the problem remains, so I'm wondering what's going on.

The only things I can think of that might be causing it are the motherboard, the processor, or maybe the power supply. I've found some relatively cheap replacement parts on eBay, but if anyone has any ideas about which piece of hardware I should try to replace first, that would be really helpful.

Thanks in advance.

 

What about the dust?
Never mind the dust on the fan itself, but you have to likely remove the fan itself to get to the area between the airvent and the cpu (which is where most dust accumulates).

If that doesn't work, then it's possible the fan itself is out of order, or you just might have dust clogged in areas you cannot reach (in which case, use a compressed air in a can).

Have you checked if the heatsink is pressing propperly on the cpu?

 

Thanks for the reply, Deks. I've taken literally every piece of hardware apart so far (had to in order to get the motherboard completely out), and dusted everything off. I clean the dust out of the fan and airvent fairly regularly, and it's clean now, so I don't think that's the problem.

When I reapplied the thermal compound, I made sure the heatsink was pressing down properly, so I don't think that can be it, either.

The only thing I can think of is some piece of hardware not working right, but I'm not sure which one it would most likely be. Is it possible the processor is getting too much voltage for some reason?

 

Is the fan working properly?
Have you measured the temperatures by any chance?

As for the voltage ... possible, but unlikely ... unless you were modifying the voltages yourself.

 

No, I haven't done any modifying like that, or measured the temperatures. I just know that the last time I turned it on, the processor went from room temperature to burning my finger in ten seconds flat, which doesn't seem right even without the fan running.

There may be something with the fan, because when it first overheated and shut down, the fan had stopped turning for some reason. But it does still turn on, and it does run most of the time, although I can't quite tell if it's running only some of the time because it doesn't need to be running all the time, or if it's because it isn't working quite right.

When I turn the machine on, though, the fan does kick in within a few seconds, and it goes straight into high gear, so I assume that's because it knows the processor is already getting too hot.

But maybe I'm wrong on some of those assumptions.

 

Without the fan, a CPU without any type of thermal shutdown will burn itself up in under 30 seconds, so that seems reasonable. If the fan turns off, the result will be the CPU overheating and shutting itself off almost immediately.

 

It really happens that quick, huh? Okay, well, when I get home tonight I'll throw it back together and see if the fan is working right from the start or not, and put an update up here. Thanks for the help so far.

 

your CPU is a P4, which would explain why it get so hot so fast.

Can we go back to the beginning.

1- Have cleaned your laptop before or was this the first time? I mean did you remove the heatsink before for cleaning and replaced the thermal past.

2- Did you find any dust when you cleaned your heatsink?

3- Have you cleaned the old thermal past off the CPU before applying the new one?

4- isn't there suppose to be a blue thermal pad between the chipset/GPU and the heatsink?

 

1) I've cleaned out dust from the fan and heatsink before, and fairly regularly, but I had never replaced the thermal compound before last week after this started happening.

2) There was a bit of dust in the heatsink, but not much since I had cleaned it not too long ago.

3) Yes, I took the old stuff off before I put the new stuff on.

4) There wasn't one on mine, and I bought it new. Maybe some similar models have one, but mine's been running fine for over five years without one.

After I got home today, I put it all back together and booted it up, and this time the fan didn't work at all, so that must be the problem. Is there any way to tell whether the fan itself isn't working or whether it's the motherboard not giving the fan enough power?

 

A processor wont burn in 30 seconds at bootup. It will take over a minute for that to happen. When a BIOS boots, the processor is at idle, it is not under full load. I have run my quad core opterons without heatsinks for over a minute diagnosing multiple processor motherboard problems. No problems resulted, and those are only rated for 70C max.

Back to your questions, yes you can test your fan. Remove the fan from the system. It will have some sore of connector which goes into the motherboard. Every laptop fan I have seen is 5V. There should be a sticker on yours which states the voltage. The fan will have a female connector on it which plugs into the motherboard. Find a paper clip. Cut it in half and jam it into the female hole in the connector. Than connect those paperclip leads to a 5V power source. It doesnt even need to be 5V. As long as its over 3V, the fan should kick in. Try different combinations if you do not know which is positive, negative, ground, or tach. You can use thin electrical wire instead of paperclips if you have.

I would be leary of a system which shuts off after 30 seconds.
Have you tried booting without a heatsink?
Put your finger on the die, then press the power button. If it gets hot, than the processor is getting power. If it gets hot, pull the plug immediately so you dont damage anything.
If the processor does not get, that indicates that the system is experiencing another issue. The motherboard could be bad, one memory card could be corrupt, or a cable in the system may be frayed or shorting somewhere.

K-TRON

 

There must be another problem, then, besides just the fan. I've booted it up without the fan or the heatsink, and it's overheated to shutdown in ten seconds after being unpowered and unplugged for 24 hours. Starting up without the fan but with the heatsink will get it to last roughly thirty seconds.

Since the processor is getting hot, and fast, does that mean it's can't be a motherboard issue, since the motherboard is supplying power? Or could it just be a specific part of the motherboard that's not working right?

 

What now? read what you wrote and it makes sense. You startup without the heatsink and the CPU overheats and goes into thermal shutdown in a very short period of time. I surprised you even got 10s out of it. This is to be expected. P4's wont run for any period without a fan. I have seen a ULV PM run without and heatsink, but then it was a 5W TDP CPU!

You then put the heatsink on and now it goes for 3x as long before thermal shutdown. It seems like everything is working as it should. The thermal mass of the heatsink means it takes longer before the heatsink gets too hot and the CPU shuts down. Why don't you try putting an external fan (such as a desktop personal fan) blowing over the heatsink and boot it up. If there is sufficient airflow it should boot and run without any issue.

It is either the fan or the fan controller. You can check with a voltmeter to see if the fan header on the motherboard is producing any output (either 3.3V, 5V or 12V) during POST when the fan should be running at full speed before the BIOS kicks-in to control the fan. If the fan controller is producing an output then it is most likely the fan is dead (and 9/10 times that is the end of it, buy a new fan and you're good to go). The fan header will probably be 3 pins - ground, power and tach input.

The other 10% of the time it is the fan controller on the motherbaord. This has happened to me and I ended up wiring the fan directly to 5V so it ran on high all the while, which was a bit annoying but essentially a free fix. The other alternative is to get a new motherboard but that is probably not cost effective for an old P4 clunker!

Good luck.

- Tim

 

Thanks, Tim. So basically the only likely culprits here are the motherboard (or at least the fan header on the motherboard) and the fan, correct?

I don't have access to a voltmeter, so I might just grab a fan off of eBay (there's a few for $5-$10) and hope that's the problem. I'll also try putting a separate fan on the system when I get home tonight and see if that helps at all.

Just for clarification, did you wire it to some 5V power source on the motherboard itself, or an external power source? If it was on the motherboard, do most boards have an extra power source like that? That sounds much easier and cheaper than replacing the whole board.

 

If you don't know what you are doing, do not try to put any other kind of fan on the header, it might be the wrong power or voltage and could damage a working fan controller. I'd try another fan on ebay and go from there. Make sure you get the one for your specific machine. Being an EE I poked around PSU section's smothing capacitors until I found the right voltage.

- Tim

 

Yeah, I found several fans from the same model on eBay.

I checked the fan header with a volt meter, and it appears to be working, so the problem must be the fan.

I'm typing this on the laptop right now, though - the fan seems to be working again, if only for the moment. Hopefully it's not an on-again, off-again problem, but if it is, I'll try just replacing the fan.

Thanks to everyone who contributed for your help.

 

Me too.

The CPU might not burn but your finger will.
A desktop with a copper base cooler, and an Athlon XP 1900+ is so hot after 30 seconds that you can't tooch the heatsink without burning your fingers.

Have the OP thought about upgrading his CPU too. It seems that theri laptop suppots up to a P4 3.06Ghz

 

My Pentium 4 is running at 3.06GHz, actually. It's an A25-S2792, which has a few upgraded components over older A25s.

And even if it wasn't, I'll be getting a new laptop in the next month or so, depending on whether or not the price drops a bit. I just didn't want to be without a computer for that time.