A friend of mine asked me to look at his laptop because it wasn’t turning on, he has an HP DV4-1275mx; I would take the build date to be somewhere between late 2008 to mid 2009 since it had a Vista sticker on the laptop.  So he turned it on to show me what was going on, after seeing the problem I knew I would be looking into the HP DV4 diagnostic lights pattern to figure out what the problem is but before I go into detail about that a computers POST(Power On Self Test) needs to be addressed.

Dealing with computers you learn how to understand hardware related problems; if you start a computer up it runs a POST(Power On Self Test), if there are any problems you hear a bunch of beeps, or you will see lights flashing in a pattern.  The output of the POST is different on computers, lets break it down with Mac’s and PC’s, we’ll start with a Mac since generally it’s easier as Apple is the Hardware and Software manufacture of its own products.

When a Mac starts its POST, you will hear a chime noise(you won’t hear the sound if your muted the computer on shutdown), as soon as you hear that you know the POST has detected all the hardware that it needs to boot up passed, if it didn’t what generally happens is you see a somewhat helpful image of something, like when a Mac has a bad hard drive you will see a picture of a folder with a question mark on it telling the technician that Mac OS X couldn’t find the files to start up the Operating System.

When a PC starts up and it begins its POST it will start to test if all the hardware it needs to boot up is good, if it isn’t well it begins to beep at you with different beep patterns, from there if you bought a machine from HP, you can go to there website and look at the beep patterns to figure out what is wrong with the machine.  With laptops depending on the manufacture there will be a series of lights that will blink, this is what I like to call the diagnostic light pattern.

Now what I have here is the HP DV4-1275 laptop and according to HP’s diagnostic lights website, if I power on the laptop and wait a bit the caps lock and num lock will blink a certain pattern, from there I can begin to troubleshoot why this isn’t starting at all.  So I wait for the lights to start blinking and I got 1 blinking light thus according to HP’s website it is telling me I have a non functional CPU! All right cool I can deal with that no problem!

I remove the hard drive, memory, wireless card, and dvd-rom drive to get the laptop down to the motherboard and I order a CPU from eBay that was tested to be 100% working, seller has 100% positive rating and mind you they were a power seller.  $30.00 bucks later and a few days pass I finally got the CPU and the first thing I did was check the pin grid array for anything that was bent, missing, or out of place and everything was fine, put everything back together for a basic start up(Protip: If you work on hardware you know that you never completely put everything back together til you know everything is working.) and turned on the power button, same error code!  Now I’m left to question if it really is the motherboard or if its again the CPU.