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Author Topic: [NEVERMIND] Broken motherboard. Is there anything I could still try?  (Read 1157 times)
Meizirkki
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July 10, 2012, 07:07:30 PM
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I bought a Dell Precision 690 today.. and broke it only 30 minutes later *facedesk*

I decided to upgrade it with two Xeon 5150's and while installing the heatsink on top of the second CPU my screw driver slipped and broke an SMD resistor from the board, R431. The computer still turned on but shut down almost immediately.

I found the resistor and measured it to be quite exactly 149 ohms. It was cracked a little so I have no clue whether this is accurate. I successfully soldered a potentiometer set to ~146 ohms in the place of the resistor and the computer turned on again and the screen started showing POST. Victorious smile on my face I quickly switched it off to put everything back in place. Once I was finished, I turned it on and after 20 seconds it shut down again Undecided

The faster I tried to turn it back on the less it would stay on. I figured this could be an overtemperature shutdown of some sort and checked all parts from heating. Nothing, everything was cold.

Pictures:
http://i.imgur.com/KGXksh.jpg

The spot: pads marked with red. (only one leg of the potentiometer connected in this pic)
http://i.imgur.com/djK4Uh.jpg

I started to randomly adjust the resistor hoping I'd be lucky. The two ic's and their external components seem to control the big SMD regulator you can see in the bigger picture, just outside the red circle. I'm really confused to what voltage it controls. The input voltage which seems to come from where the RAM is located, is 1.5V. Output voltage of the regulator depends on the setting of my potentiometer. The output voltage can be anywhere between 0-1V and the computer will run for some time. When the output voltage is over one volt, the computer turns off almost immediately. The max output is 1.18V and possibly not stable (may be the reason for quick shutdown) Any ideas to what the voltage should be and what it is for?

Thank you in advance for any ideas and help to the right direction!

EDIT: I just noticed from the picture there is a broken via next to the electrolyte capacitor! *tingles of hope*
EDIT2: Sigh, nope. Via is fine, it was just a piece of tin
EDIT3: Mother of god. 0.33 volts did it. It works again (for at least 3 min Tongue )
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