Inspiron 1520 Black Screen on Boot

[jinjin12]

my inspiron 1520 is getting a black screen when i boot and it just stays black. i did a display test on it by holding D and the power button. the display test was a success so it's not the display's fault. i'm pretty sure it's the GPU, because i've tested it by trying to hook it up to an external monitor and nothing showed up. but before i waste money on a new GPU, i want to know:

1) how do i test the motherboard to see if there is anything wrong with the mobo?

2) how do i start the laptop so that the POST codes will show up? i'm talking about these codes here http/www.bay-wolf.com/portpostcodes.htm i don't know how to get those codes to show up cause they can help me alot. is there a certain key i have to press to show in that mode?

thanks a lot in advance.

 

[C12Friedman]

Testing a motherboard is not easy (harder with a laptop mobo IMO) and can be very time consuming. How to is quite a bit more in depth than I would want to get into here but searches may prove to be helpful
The lights should blink within a few seconds of the computer powering on, nothing to do, just watch the lights.