I was given a non-working laptop and told that if i could fix it i could keep it. The power supply checked out. So i opened the laptop and discovered that the side vent that leads to the CPU fan was completely clogged. So I think the CPU may have OVERHEATED and is no longer working. But I decided to replace the motherboard and the CPU fan. The CPU fan is connected to a copper heat sink arm and one end it sits on top of the CPU. I know that the ram is good as well. I put the Laptop back together make all the connections. When I turn on the LT ( I attached the keyboard but left it up so i could see if the CPU fan would work.) But now the green power light and the CPU fan comes comes on but only for a few seconds then stops. The LT keeps doing this over and over again but the LT NEVER starts or boots up. I get no image on the screen either. I know the hard drive is good. What else could it be ??


Some of the laptop specs are: Sony Vaio PCG - 71312L 5GB HD, 4096 Ram, Windows 7, Core CPU



Albert O.
Well you went down the correct troubleshooting path of verifying that the CPU fan moves and that if it moves then it cant be the cause so where else to look. My thoughts on this is that the laptop likely overheated cooking a component creating permanent damage on the main board as a result of this. The CPU is protected both by the watch dog circuit of the tach on the fan that as long as the fan is spinning to keep the system running but if the fan isn't moving then shutdown the laptop without warning ( hard shutdown ) and power off to protect from damage as well as the CPU itself has internal thermal protection to perform what is KNOWN as Thermal Throttling when it gets to a certain threshold for a temperature to which it will work with the main board to underclock itself to slow its processing as a MEANS to reduce heat.

All other components on the main board do not have such thermal protection and so they are subject to roasting and cooking themselves to death if there is a lack of cooling ( airflow ).

If it was a laptop given to me which I have been given many dead computers, I would salvage the CPU, RAM, and Hard Drive from it and if it has a DVD ROM check to make sure no Discs are in it. Toss the rest into recycle and save these parts for another laptop that could be acquired cheaply or for free that use these components as an upgrade to it. The CPU however in another laptop would be tricky however as for its more of an advanced upgrade path to where you have to make sure the main board supports it and that the TDP of the CPU your putting into a healthy laptop main board is very similar to the TDP of the CPU coming out of it, otherwise the cooling of the CPU could be inadequate and lead to thermal throttling and a CPU that's running in excess of 80C.I did replace the Motherboard.


Albert O. Thermal paste applied proper ? ?My Bad in not seeing this initially...
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But I decided to replace the motherboard and the CPU fan.