Motherboard repair

Chances are it's an N-channel power MOSFET, look for the regulator controller chip nearby and look up an app note, it should have a reference design with suitable mosfets.

"James Sweet" skrev i meddelandet news:%UL%d.14909$UV2.664@trnddc04...

It seems that the AX6BC is equipped with smt mosfet and the AX6B with ordinary hole mounted with heatsinks. On mine AX6B one of the mosfet transistors were burned but those were CEP6030L with TO220 package but for AX6BC I think they use D2-pak. Replaced it with another CEP6030L and it is still running. RC5051 is used as programmable synchronous buck controller. You might be able to check the drive to those two mosfet transistors. Download the application note AN-53

interesting reading.

Bjorn

On 21 Mar 2005 17:32:25 -0800, "Mr. Land" put finger to keyboard and composed:

Can you locate the part in this photo?

Is it in the top LH corner? If so, then check the nearby capacitors for signs of leakage or swelling. What is the part number and logo on the IC to the left of the lower 4 caps?

- Franc Zabkar

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for

small

You can buy a complete board on eBay for $15. How much is this worth to repair? I know, it is the principle of the thing but your time has value too. GG

What about the educational value and the satisfaction of repairing something? As others have pointed out in the past, this isn't sci.electronics.replace.

I've been getting satisfaction for many years repairing.electronics. Also, have done some design as well but when you're talking $15 to replace something or spend several hours working on multi-layer boards that may have internal burned traces and other bad components AND no prints, why bother? My time is worth more than $7.50 an hour. I assume yours is as well. Its not like you're restoring a collectible item that merits the TLC. I'm done GG

Hi,

Thank you very much for your response. Unfortunately, even though I've dabbled in electronics in the past, this is sounding like I'm in a bit over my head...I don't even know what "look up an app note" refers to.

But thanks for trying to help me.

Cheers.

I went to read your reference...hmm, looks good, but way over my head!!!!

I did manage to notice in their sample circuit the two mosfets in series, and since as I stated originally there is a second device (which is OK visually, at least) with the same part number, this might indeed be close to what I have.

FWIW, since I had nothing to lose, I took a wild (in retrospect) guess that it might be an NPN transistor and tack-soldered one I had lying around. The BIOS booted! But as soon as it tries to read from the boot drive, it either states there's a missing file, or it can't read it at all. So I guess the NPN was a bad guess!

Also in retrospect I'm pretty lucky I didn't blow the whole thing up!!!

Thanks a lot for your help!!!

Actually, thanks, I did indeed acquire a replacement on eBay.

But when I look at that board, all the parts on it, it just seemed like such a waste to just toss it.

Thank you for your reply.

Yes, I can see it! This is cool!

I had to load your picture into a graphics editor and zoom in a bit. But here's where the failed part is: to the right of the PCI sockets there is one large, square IC that appears to have some kind of orange-colored mark on its upper left hand corner. If you sight along the top edge of that IC, and move your gaze directly right, you'll come to 2 electrolytic capacitors standing next to each other; just below those capacitors is a row of small surface mount components, some caps, some resistors I think. If you sight along this row and continue moving your eyes to the right, you'll come to a white dot. That is the metal (heat sink?) tab of the device that blew out. The body of the device is above that, and the 3 connection leads are just above that. If you go back to the 2 electrolytic capacitors, and look directly above the left one, you'll see the other device that matches the one that burned up.

Hey, thanks so much for taking the time to post this picture!!

If you got that close then it's almost certain that replacing that one component will fix it. Try an N-channel mosfet.

I can't explain or justify my desire to fix this board.

All I can say is that when I go to drop it in the trash barrel, I look at all the components on it and the work that went into making it (ok, well, my board and 99,999 others just like it) and I think that I may be chucking it all because of 1 little component, I can't bring myself to do it.

You're right, I guess that's pretty silly. But I also think that if I manage to fix it, I'll feel good about accomplishing that, even if the $$$ doesn't weigh out.

Thank you for taking the time to reply.

Where would an ordinary person like myself acquire one of these CEP6030L's in the D2 package?

Thank you!

FDP6030L from

should do the trick for you, might even be able to get a free sample from Fairchild.

On 24 Mar 2005 20:18:06 -0800, "Mr. Land" put finger to keyboard and composed:

The advice you've received so far is for the MOSFETs to the left of the CPU slot. Clearly you have some other fault near the southbridge. Does your component have a circuit reference, eg Qnn (transistor nn) or Dnn (diode nn)? Judging by the copper tracks, it appears that your transistor (?) is driven by the IC below the second capacitor. If I'm right, and if you can identify this IC, then its application circuit may reveal the function of the transistor.

- Franc Zabkar

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Yes, there is a Qnn number near the blown component. Unfortunately, right now I'm at work, and the board is home, but I will post that number later tonight.

Also, yes, while I was tacking in the NPN xstr, I did notice that the foil trace for (what I thought was) the base lead went down to the small IC below and to the left. That IC is an LM324 (I remember it because I recognized the number.)

Thanks again, folks!

Thanks. Looks like the FDP6030L is a TO-220 package, while the FDB6030L seems to be the smaller "D" package which I believe was on the board originally.

Unfortunately, it seems the minimum quantity for the FDP part is 45, for a total of just under $40. Think I'm heading for a dead end...

Thank you.

Spoke too soon, found one at Mouser (in the right package) for $1.50. Thanks!

On 25 Mar 2005 08:13:31 -0800, "Mr. Land" put finger to keyboard and composed:

The "nn" is not important, it's the "Q" that tells us that the component is indeed a transistor of some kind. A "diode test" of the good part using your DMM should identify whether this is a BJT or a MOSFET.

An LM324 is a quad opamp. I have no idea what its function would be on this board. OTOH, an LM3524, a PWM regulator, might make sense if there was a coil nearby, but I don't see any.

- Franc Zabkar

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