Laptop starts and turns off after dust cleaning

My laptop dell 1525 would turn off after a heavy session of watching youtube for 10 minutes so i decided to clean the cooler. Since i didn't have any thermal paste to replace the old one after taking off the cooler i just removed the dust that i could reach. I turned on my laptop but it still turned off after a short period of time. So today i bought xigmatek pti-g3606 thermal paste. I wanted to take out the ventilator so i took off the keyboard, cooler, palm rest, hard drive, optical drive, cpu(to clean off the old paste). I took all of that off to see that to take out the ventilator i had to take out the motherboard, so i decided to leave it in there and just blew off the dust that i could reach. I put it all back together and clicked the power button. The fancy leds start flashing like normal, the hard drive and ventilator rev up to normal speed, but the lcd doesn't turn on. After a few seconds it turns of like i forced it. I tested the sata HD on my desktop and it all works normally. I don't know what and how to check next. Maybe i hooked up a connecter bad but i double checked and don't see anything.

Small update:
-when the laptop is turned on only with the battery the above actions are displayed.
-when the laptop is turned on via the power grid(220v) with or w/o the battery this happens: It powers up and turns off after a few seconds. And all of a sudden it turns on again so i left it on like that for 5min before i forced it off. I hooked up a analog monitor and there is no signal going through to it. The HD led doesn't show anything be written of read off of it. The hard drive and ventilator are both working normally.

 

When you put the CPU back in the mobo are you sure it was seated correctly and the socket was locked tight?

You could try re-seating your ram too.

Also double check your display connection.Make sure its tight too.

 

Triple checked the display conectors but why would the extra power from the grid make a difference in the actions that happen. CPU Socket is tight. Will check the ram which i didnt touch ASAP.

What does it look like when the ram is the only problem?

 

Just checked the ram. Each module in each slot. No differences.

 

Remount the heatsink, make sure you have solid contacts. Also, make sure you didn't bend on pins on the cpu.

I'd also check all your connectors and wires to make sure you didn't break any solder joints or inadvertently crimp any wires.

If it's not POSTing, I'd also pull the CMOS battery, short to socket, then reinstall that.

Worst case, I'd also check all the caps to make sure none are blown or leaking, and do a very careful inspection of the CPU and GPU contact surfaces on the heatsink to see if you've got bubbling or bad contact.

 

If the heatsink isn't mounted correctly won't it turn off after heating up pretty fast?

I called a local computer servicer and he said that its most likely the GPU that needs to be replaced. Can anybody confirm that this is possible?

 

I left the laptop at another local servicer. He says that i may have broken the CPU. When we took out the ram there were no beeps at all?

 

You ma have toasted the CPU through multiple power-ons if the heatsink wasn't making proper contact. Same with the GPU. Most laptop heatsinks come with a thick (0.5 - 1.0 mm) paste to contact the CPU/GPU and need a shim to span the gap to make proper contact. Your themal paste might not have been touching the chips at all.

If you're unlucky, you bent pins on the CPU. Sometimes you can bend them back, but odds aren't good that it will work properly after bent back.

If you're really unlucky, the heatsink wasn't tightened evenly and you cracked the chip somewhere.

 

Well all i can do now is wait for the servicer to call me in ~15hours and tell me what it is.

 

Ouch!!

Sorry to hear that...