Maximum PC

Gir... I feel a conspiracy *sigh*.. not really, but this is just plain wierd:

My girlfriend and I bought ourselves 2 HP laptops 3 years ago, almost at the same time. My was HP HDX 16 (X16t-1200), and Her's is HP Pavilion (HP Pavilion dv4).

About 3 months ago, Pavilion would have a black screen on boot (the back light will be on, but no image, so its't not a bad inverter). However I don't think that it is a display issue at all, because after waiting I won't hear any windows sounds. It seems like computer won't even POST. Trying to get into BIOS won't work either. However the problem would go away as random as it'd appear - screen would start working all of a sudden. It happened again yesterday, and it's been off so far... Any ideas what could that be?

Also yesterday, my laptop stopped powering up at all. Not a single light would come on. So I took a CMOS battery out. waited a bit, and put it back in. How the lights come on, but it won't POST. On power up I just get blinking Caps lock and Num lock. This is some HP's feature to indicate hardware failure, but every website I found says that there should be maximum of 8 blinks, and this thing just keeps blinking forever, until I hold the power button to shut it down.

I found a few suggestions and tried simple fixes
Remove the battery, remove the charger, hold power button for 10 seconds, plug the charger back in. Power up.
Removed all components like HDD and RAM, neither computers would POST.
Took both of them completely apart, and put back together, hoping it was some connection issue, but nothing changed.

So i'm out of ideas and really frustrated. HP Customer service wants 350$ per computer to fix it, and it's just cheaper to buy new one. Any ideas will be appreciated. Thank you. Hexorg.

I bet the DV4 has a Nvidia chipset for the graphics, if it does you might get HP to repair it free of charge.

http://www.engadget.com/2008/07/31/figuring-out-which-nvidia-gpus-are-defective-its-a-lot/

Ah well actually I found the problem in Pavilion. Apparently a bunch of people have it, I just wasn't googling the right thing.

The display cable goes through a hole that's smaller then the cable and it gets pinched every time, breaking the cable. I just ordered a new one of ebay and will fix that soon

Now only to figure out what's wrong with my laptop...

That is a possiblity, but anything manufactured between 2007-mid 2008 will eventually fail due to bad solder underneath the nvidia chip, If that cable doesnt work, take it down and get it either reballed or reflowed(best is reball to remove the crap solder.... but reflowing can work for a time)

I would also test the RAM individually, and in one slot at a time.

Ok, both computers are fixed now. In Pavilion, the cable was broken, after replacing it, everything works like a charm.

In my HDX16, something bad happened to the motherboards, after buying a replacement on eBay, I got it back and running. Thanks for advices everyone

P.S. Anyone knows someone who buys broken motherboards?