No POST on Pavilion zv5000

A long post, I know, but I wanted to get all the details in. My brother sent me his zv5000 laptop to try and repair the power connector. He said that it wouldn't charge the battery and that he would have to move the plug around to get power. After doing some research, it seemed like a bad power jack, which is a very common problem with HP's. So I took the laptop apart and checked out the connector; it seemed fine. When I put it all back together, it wouldn't boot. My brother said that it worked before he sent it too me and I forgot to try it when I got it. The power LED and all the lights on the keyboard would turn on, the processor fans ran for about 3 seconds, then shut off, and there was no display or HDD activity. I figured, the motherboard probably died, which I was going to replace anyway. After getting a used one from Ebay, I put it in the laptop and it did the same thing. So, I grabbed a different processor and tried that. No luck. I have gone so far as to take the board completely out of the laptop and with just power and the display hooked up, no RAM, no HDD, no keyboard, and tried to boot. Nothing. I have also tried using an external monitor, with no luck there. The only things that have been common are the processor fans/heatsink and the power supply. The power supply voltage checks out ok, about 18.5Vdc. I am really at a loss as to what it could be. Is there some reset on the board that I am missing? I really don't want to put any more money into this thing. My brother doesn't really want it back, but I want to try to figure it out anyway. Any help would be appreciated.

I have not tried a different power supply, but I did measure the output voltage. It was 18V like it should be. If it is something on the board, why are both of my motherboards doing the same thing? Could my power supply be failing under a load?

I have tried many different RAM chips in both memory slots, but this doesn't make a difference. The LEDs stay on until I power down the laptop. The thing that gets me is that both of the motherboards and processors do this, in any combination. Do I need to have any RAM installed to boot this thing? I have also tried booting with and without the LCD display connected. Still no POST. Could it be that the CPU fans aren't being detected? Would this cause the laptop to stop its boot process?

I hope it's something simple. This is the big reason I don't really like laptops; you can't take out different parts, such as video cards, power supplies, etc. to see if one may be bad. Who knows? Maybe these boards are super sensitive to ESD, and Stagger, you and I zapped ours. Maybe there's some secret procedure know only to HP techs that make these things work...

Really? When I removed the cpu, it did come off with the heatsink. I will try and unlock the socket tonight. Trying to install into a locked socket won't damage the cpu pins, would it? I'll post my finding later tonight.

That was it! I locked the CPU in, put in some RAM, and viola, bootup! Thank you so much Ikenfixit! I would have never even thought of checking for that lock. Give it a try Stagger, I think that'll do it.

Yeah, it seems like the pins were not all the way in the socket. You have to remove the CPU from the heatsink so that you can turn the locking screw and secure the CPU. You may need to turn the screw one way, place the CPU in the socket, and turn the screw the other way to lock it. First, though, clean all that gunk off of the CPU and heat sink with some alcohol. This is thermal paste, which conducts heat between the CPU and heatsink. You should be able to pick this up and any computer parts store. Apply a small amount (just enough to coat the CPU when the heatsink is tightened down) of new paste before tightening down the heatsink. Slap in some RAM and you should be ready to go!