Reassembled laptop won't boot

Hi, I took apart my Toshiba A200 because it was overheating and turning itself off, also high cpu usage although no processes were using more than 2%. Removed a large carpet of dust from heat sink. Reassembled, having cleaned old thermal paste off cpu and replaced with new.

It seemed a strange arrangement for me with the thermal paste between the chip and a thin sticking out aluminium part of the fan housing - but then I've never taken apart a laptop before, only PCs.

First try, it got to the 'Toshiba' screen but turned itself off before getting to any windows screens. Took out and replaced RAM. Now it gets to the windows loading screen with the progress bar - does that for a while (doesn't show windows icon though, a bit odd...) and then turns itself off.

Tried this several times, one time got partway through the windows 'your computer didn't boot up properly, checking for problems...' wizard thing, it lasts different amounts of time each time but always turns itself off abruptly.

Looks to me like it's overheating way quicker than before, so I've broken something.

Could it be the thing that is like a sticky aluminium foil that connects the fan casing to the heatsink, I had to take it off to get at the dust and it wouldn't stick back on flat. Or have I somehow managed to dislodge something under the motherboard, although I didn't take the motherboard out to get at the underneath. Or should I try jiggling the RAM some more. Or give up and pay someone who knows what they're doing :-o

 

Unfortunately, it appears the motherboard, CPU or GPU suffered excessive heat damage before you took it apart and cleaned it.

I run into a few situations like this on units brought in for repair each month. At this point the damage is done; no amount of air duster or thermal compound will cure it.

Sadly, if you want to fix it, you'll have to get another motherboard or find a tech who can troubleshoot and repair the existing one. The latter option is iffy; if you go this route be sure the tech gives you a written warranty on the work.

 

Aargh.
Thanks for your response. The only thing that makes me wonder, is that it only shut down intermittently before - it might last a couple of hours, or at least 20 minutes. Certainly longer than it does now. Which makes me suspect something that I've done... and if I replaced the motherboard I might do it again...

 

Although anything is possible, my response is based on several years of repair experience.

Each time the unit overheated and shut down before you took it apart, a bit more damage was done. On units I've attempted to clean or replace the fan on (as you did), there is no set time on how long the PC will power up before shutting down. At best, I've seen 30-45 minutes. At worst, it won't even get through the BIOS post to start loading Windows. Either way, there is no sure-fire fix other than replacing or repairing the board.