why is my laptop doing this?

I have an old alienware 5620d.

here are the specs:

P4 2.4ghz 512mb cache
512mb ram (1 slot)
integrated ati radeon m9000 (128mb)
cd-rw/dvd combo drive
80gb hdd

here's the problem:
5620's are notorious for getting really hot and frying the videocard which is stupidly integrated on the motherboard. I was lucky enough to find someone selling a couple BRAND NEW motherboards for a good price ($120). I picked one up, took my laptop apart (I've done it a couple times), replaced the motherboard, put everything together and plugged it in.

When i plugged in the power, the power indicating light turned on as well as the battery charging light. I pressed the power button and it goes to start up for 4-5 seconds, then shuts off.

Took laptop apart again to make sure everythign was connected etc. Tried to turn it on and the same thing.

Tried resetting the bios on the motherboard by unplugging the bios battery for 30 mins. Tried to turn on again and same thing.

Tried switching the ram to the other slot, no help.

I bought a new power supply for it, and it is doing the same thing as the old power supply. Tried it without a battery, just powered from the outlet, no help.

The battery is dead, because when I try to turn it on without wall power, it doesnt try to start at all.

Also, I can't get the battery to charge, if that effects why it isn't turning on.

Could it be that my bios battery is bad? something else? I'm so out of ideas my head hurts. This quick fix has turned into a terrible headache.

PLEASE HELP (sorry for the long post)

 

Could be so many things including a bad MoBo.

 

so many things? I read elsewhere that alot of the time this happens because of a loose lcd connection? does that sound right.

The mobo i got is brand new. Before, the computer would turn on completely, just no video or external video because the card was fried. Now, blinking led's and 4-5 seconds of power.

could you elaborate what the problems could be so I can try them.

Also, does anyone know a laptop repair place in south eastern pennsylvania?

 

bump, need help!

 

So many things...
1. try it in a different outlet, in a different building.
2. Look online or phone alienware and see if the laptop needs a battery in it to turn on.
3. Make sure it is dust free.
4. Check the power plug's connection to the motherboard and make sure it is soldered on properly.
5. Make sure the power button is working properly. I'm not quite sure how to check it. Look online and see if anyone has had a problem with your laptop and the power button.
6. Check the connections with the status light LED's, make sure they are soldered properly.
7. Remove your ram and attempt to power up the machine.
8. Remove the CMOS battery and attempt to power the machine.
9. Remove the hard drive and try powering it, remove the cd drive and try powering it (seeing if one of these components is causing a short, forcing the computer to stop to prevent damage).
10. Make sure every screw hole has a screw in it in your entire computer.
11. Try a new battery.

Did you use an ESD bracelet when you the motherboard etc. in? You may have damaged it via static electricity, and if so, you would be hard pressed to find the cause of the problem. Remember that you can still pass a deadly (for electronics) shock of electricity without feeling or seeing it.

Considering it starts up then shuts down, it is probably a short, the processor or mobo thermometer is jumping off the scale so your computer shuts down, or ESD has damaged something critical somewhere on the board.

GOOD LUCK!

 

In addition to Lt.Glare's suggestions, make sure the processor is seated on the motherboard correctly, and check the cooling system is correctly fitted. Its difficult to say what the problem is, as it could be the motherboard or a number of other components.