Laptop power-up conundrum

[course2kid]

I have a Sony Vaio VGN-FW170J laptop with a weird problem. One day it will be operating flawlessly and the next day it won't turn on. This is definitely not a powerjack or AC adapter issue - the motherboard always has the 19 VDC input as verified by DVM.

Here is the weird part... when the unit fails to power on, I unplug it, pull out the battery, the ram, the optical drive, and the SDD, and remove the bottom case. I put it all back together and the laptop works fine for anywhere from a day to a month and then stops again. I repeat the disassembly/reassembly process and it works fine again.

Another thing that can be elimated is the lid closure sensor. The laptop can be open continuously for days without even being moved and it will still go from working to non working. Also, I've played with opening/vlosing/tapping the lid and this has no affect on getting the unit to turn on. Also, the unit never turns on with lid closed and the screen goes off when the lid is closed, so, that sensor is working as it should.

Any thoughts on why I get an intermittent power-up failure that is cured by dissassemby/reassembly?

 

[Scottray]

The disassembly/reassembly is the key. Somewhere there's a connection just barely making contact. Then with thermal expansion/contraction and minor movement of the laptop, the connection opens up. You'll need to remove/reinstall one component at a time to try to determine which one is the culprit. Also, check all the other ribbon cables and connector to the motherboard and make sure that they're firmly connected. When you find the problem component, check the pins/connectors for wear, bent, etc.

 

[course2kid]

Scottray,

Thanks for the quick reply.

Right after I posted, I once again disassembled my laptop and, after a lot of fiddling around, I decided to swap out the power button. It's a four wire device with some LEDs and a microswitch on a very small PCB. It plugs into the "Media Board" which, in turn plugs into the Motherboard. I had previously changed out this switch a year ago when I had a different problem with the laptop and it had made no difference to that particular problem, so, fortunately, I kept the original switch. Since I put it back in, the laptop seems to power up more reliably. I guess only time will tell if this was the real problem.

With regards to your suggestion, I had previously disconnected/reconnected all the interconnecting cables to clear off any oxidation layers and that had no effect. I also checked all the metal "fingers" on the bottom case to make sure they were making good contact with their mating pads on the Motherboard.