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 Post subject: Overheating
PostPosted: Fri Feb 25, 2011 3:54 pm 
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I have a machine that boots up ok btu then freezeswithin 30 seconds. Iv'e changed Power supplies, processors and memory but no help. The fans are all going fine and I've also changad heat sinks as well as the case is open in free air. Is there anything on the Mb that could cause this?
Thanks.
Kevin :?


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PostPosted: Sat Feb 26, 2011 10:26 am 
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Are you sure its overheating? Most new bios' have temperature sensors. I'd go into the BIOS and put it on that screen to monitor the temps.
It'd show you also if its a windows/software or hardware problem.

I'd check the thermal goop between the cpu and heatsink. Maybe its not clamped down well enough or there is a gap between the two. Should be a snug fit. Also the heatsink might not be adequate for the job.

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 Post subject: overheating
PostPosted: Sat Feb 26, 2011 11:20 am 
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I checked as you suggested. Temp rises from 55 degrees c. to 68 c. in about 10 seconds. This is the 2nd heatsink i've tried, it's a tight fit but I have no thermal goop. I should explain this system ran for some years fine. When I began failing and I opened it up the orig. H.S. was totally cloged up, ( I'm a heavy smoker.) I cleaned it up and began changing parts About the onlt thing still original is the Mb. Thanks for the response. Any other suggestions greatly appreciated. :?

Kevin


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PostPosted: Sat Feb 26, 2011 3:10 pm 
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No matter how finely machined any two surfaces are, there are still many voids that prevent 100% contact. A "lapping" process may smooth the surfaces more, but will never achieve totally flat planes. With a CPU, heat transfer must be optimum. That is the purpose of thermal grease or a thermal pad. Any electronics store should have a small tube of thermal paste you can use. Both contact surfaces must be cleaned totally of old material, use of rubbing alcohol or over-proof Vodka can be used. Then a very small amount of thermal paste applied and spread across the surface of the CPU.
If the original thermal mass was a pad, then a pad must be used. Use of only thermal paste will not allow the heat sink to clamp down to the CPU heat spreader as intended, causing a rapid thermal run-away and possibly damaging the CPU. If, as you note, the CPU temperature rises very rapidly, that is a sure sign the thermal transfer is not optimal. The heat sink fan should spin with no drag. Move the blades with a toothpick. If they jiggle to a stop, all is good. If they coast to a dead stop, the fan bearing lube has dried out.
It takes less than 5 minutes to remove the fan, peel the back label, and work in some oil to the bearing under the rubber cap.. then blot out the excess and reinstall it. Use any light machine oil, such as 3-in-1 or sewing machine oil. Don't use WD-40, as it does not have the lubricating qualities needed for motor bearings!

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 Post subject: overheating
PostPosted: Sat Feb 26, 2011 4:22 pm 
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Thanks for your reply. That all makes sence to me. I'll get some paste and check the fan to see if that will do it. If those thing don'w work I'll get back to you.
Kevin 8)


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 Post subject: overheating
PostPosted: Mon Feb 28, 2011 11:27 am 
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Well I tried the thermal gel and the fan is fine but the problem remains. Any other suggestions why the CPU would overheat? :?
Thanks
Kevin :(


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PostPosted: Mon Feb 28, 2011 2:30 pm 
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Would be worth the time to see if your CPU is healthy by testing it in a mobo that is compatible with it. Modern CPU types are more complex than older ones, and are less forgiving if run at higher than recommended voltages.
There are several different voltage needs for the modern CPU types, and regulators near the CPU socket should be inspected for signs of overheating or blistering.. indicating faults. And if an electrolytic capacitor goes bad, it can "bleed" voltages into other circuits, or cause ripple in current feeds that should be pure DC.

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PostPosted: Mon Feb 28, 2011 3:48 pm 
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:o I appreciate your quick reply. Now I have to back peddle a lot. I went back and rechecked on your original suggestion and found I'd failed to check the heatsink for cleanliness. It had a lot of old gunk on it so I Changed to another after a thourough cleaning and the problem seems to be resolved. I didn't use vodka though :D Thanks again for your help. :lol:
Kevin


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