P7805u new ram and clean heat sink. Now won't start.

I got 8gb crucial ram for my 7805u. Installed it. Cleaned the fan with qtip and 90% alcohol. Took out heat sink and removed 1/4 inch thick layer of dust. Reinstalled heat sink. Restart. Black screen. Reinstall original ram. BlCk screen. I hear the HD crank and some initial processor sounds but it stops. Fan on right (GPU fan?) Is on but fan on left does not. Read the other thread and I can power off by long pressing the power key and fn+f1 does toggle lights.

Two notes.
I just bought a new 7805 but its at the house right now and I am not. I just replaced the ram in it with no prob. Except today's ram cam from a different company.

While I was cleaning the heat sink I noticed that thrwre wee numbers by the screw holes. I took #5 off first and the little spring screw does not go back in all the way.

Thanks

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I do know when reattaching the 5 screws do need t make proper contact. There was a guy with a P7801u early on that had that 5th post break from the MB and could never get the system to boot again..................

 

Update:
I switched heat sinks. Dead machine still dead. New machine boots no prob.

Screw #5 is same one both heat sinks.




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What can happen is the post can twist causing the contact to break. Other issues could be the contact of the CPU, meaning it has to be pulled and reseated, or if using a conductive heat paste it is causeing a short. Another problem could be oils or other debrise corrupting electrical contacts.

 

you may need to check speaker wires one i redid m/b in had been routed too close to silver tab by keyboard when youd tilt computer itd go off instantly caused me a little stress nothing major tho. make sure all ribbons are correctly all the way in and check where power jack is, is it totally dead or makes boot sounds? try external monitor, and when tightening screws dont tighten one at a time down do them a little bit each at a time thats why the posts will break off it puts it in bind and post pops i think you may be able to solder posts back on. but dont break one to find out lol

 

tan i think we put his computer back together pretty much lol oh if u get pic on external monitor shine flashlight on screen if you think its fully booted n see if you can faintly see screen if so backlight or inverter is bad usually backlight there a to replace ive done 2 i have nightmares from it on the old 1920x1200 screens. i have 1 m/b that does just like yours does all the fans lights just no video its the video card nvidea on mine... figures most expensive part it artifacted till it got to no video at all.

 

Thanks for the suggestions!

Took the machine to a tech this week but he was an idiot.
I've been busy this week but will take the machine apart next week and let you know back with a report

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Hi, try to use only one ram. Then in different slots. I had an issue with the laptop not opening and it turned to be the ram modules were in slots that the pc did not like. Try to simply swap them on their slots

 

This resolved the issue.
I changed the slots of the old ram and it booted . Put in new ram. No boot. Change slots. Boots.
Crazy.
I also opened the case and cleaned the GPU fan and heat sink with no problems

Thanks to all who made suggestions

I'd really like to ask an elec engineer why this problem would exist. Aren't both chips the same? Especially the new ones?

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Usually it is the reading of the SPD.........................

 

I have this same model of laptop and did the same thing as the OP did---bought 8 MB ram chips (matched) from Crucial Memory, and today cleaned the heat sink when I opened 'er up, installed the chips without incident---then couldn't get the unit to boot. Searched Internet for solution, found the one here...

So, opened up unit, swapped the chip positions, and voila, it boots up again. What the hell, eh? It worked, I'm grateful, but why do identical chips need to be in seemingly arbitrary positions to work?

Thank you for posting this, even if the solution---albeit gloriously simple---doesn't make sense.

 

So you purchased 2x8gb sticks and got it too boot with a total of 16 GB ram?