Need help to recognize a burnt chip on x200 motherboard

[pavel82]

Hello,

I recently bought a new 9-cell battery from ebay, but after working 3 hours or so with this battery, the laptop started emitting a burnt smell and stop working at all. Although, it works from AC power without the battery. After that, I took apart the laptop and saw that one of the chips is burnt which is probably responsible for power regulation. You could clearly see from the image that circled chip. http://postimg.org/image/p5rej30tj/.

Could you help me to recognize this chip, please? I would really appreciate it.

Thank you.

[rkawakami]

Welcome to thinkpads.com!

From the looks of the device I would guess that it is a power MOSFET, very similar to the one like this in the black circle: http://www.kawakami-ca.com/ibm_t2x/let.jpg

If you can tell us the U (or possibly Q) number that is printed on the board next to that device, we may be able to determine the exact part number. For example, there are three other parts in your picture that are like the one that is burnt; U5, U8 and third one I can't read. The marking for the burnt part may be under what looks like a plastic sheet.

[pavel82]

Thank you rkawakami.

Sorry I din not mention the number. It is U4.

Thank you very much.

[rkawakami]

According to what I can find, it looks like the part is a Fairchild FDS6298. A 30V N-Channel Fast Switching Power MOSFET. A datasheet is here: http://www.fairchildsemi.com/ds/FD/FDS6298.pdf

You may also want to check fuse F8 as it's between the MOSFET and the battery terminals but in many cases the MOSFET will blow up before the fuse does. There's also a chance that whatever caused the MOSFET to destroy itself (for example, an electrical short somewhere else on the motherboard) still exists and that the new MOSFET will do the same thing. Good luck!

[pavel82]

Hello rkawakami.

Sorry for the delayed responce.

With your help, I got and replaced that burnt chip and the laptop works with the battery again!

Thank you very much for your help.