Asrock Z77 Extreme4 help needed to identify damaged transistor/diode

Thank you Lutfij

You're right and I agree with you 100%, considering the soldering/electronics experience of the average users. But I had to repair this board

By the way, the original transistor fell of after being touched with the pliers I was using to help me unscrew the 212x. It got off so cleanly, that it left the solder on the board (it was a little dull, so it might be a cold joint).
Hadn't I heard something hitting the case plate, I wouldn't have noticed that the transistor was missing.

Disclaimer:
If anyone else tries to do the same I'm not responsible for the consequences. If anything goes wrong and aditional damage is caused, it is the user's fault. Motherboard repairs should only be attempted by someone with the required electronic notions and soldering experience/hability .


Now, returning to what happened.
After this little accident I tried two other boards with no success:
An Asus P8Z77-V Pro, bought form e-bay, that arrived with damaged socket pins (one of them broken, several others bent), and a busted Wi-fi connector. I ended up straightening the bent pins, but the broken one prevented the use of 2 of the ram sockets (no dual channel possible), fortunately I was able to get a refund;
Next, I was able to buy in my country, from an online store, a new old stock Gigabyte GA-Z77-D3H, and that was even a worst experience: with the stock bios I was unable to boot with my Asus GTX 970ti, and even after flashing the bios I was unable to use it stable, it ended up in endless boot loops. Fortunately I was able to return it and get a refund.

With these bad experiences I decided to bite the bullet, since that even without the transistor the board was stable and better than the other two I've triend.

I did some research, and from the silk screen-codes normally used in PCB's Q7482 could only be a transistor (Q). Then, after further investigation I narrowed the transistor W04 21 to a 3904 NPN transistor (http://www.s-manuals.com/pdf/datasheet/p/m/pmss3904_nxp.pdf)

After some probing with a multimeter, I found that the base from Q7482 is connected to the collector of Q7483. So, after failing to repair the lifted pad I ended up soldering a regular 2N3904 to the board with a jumper cable from its base to the collector of Q7483.

I've repaired the motherboard almost two months ago (on the 17th of May) and the computer is working fine, with the I7-3770k overclocked to 4.4ghz, and in June I upgraded the ram from 16 to 32 GB.

Let's hope I was right in the troubleshooting/repair.


Two lessons I've learned from this experience:
If I'm unable to unscrew the cooler with the board on the case (the two lower screws aren't accessible through my case motherboard tray), I shall not try to take it out the easy way, and will remove the motherboard from the case first;
If I don't have my regular soldering tools at home, I will not try to do repairs on motherboards with a cheap 3€ soldering iron ... never again.

Patient pays off.


By the way, I do my own repairs on my vintage computers and consoles (recaps, sockets and chips replacement and other mods), the big difference is that the motherboards nowadays are heavy smt populated, being much cheaper to produce but significantly harder to repair (you are supposed to buy a new one and throw the damaged part to the recycle bin ) .

Here are some photos of the work I've done
http://s000.tinyupload.com/?file_id=03167696784550648681
http://s000.tinyupload.com/?file_id=95464111238735924099
http://s000.tinyupload.com/?file_id=40630345745316230640