Help Identify this blown chip on Thinkpad X61s please

X60/X61 series specific matters only.
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jkn
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Help Identify this blown chip on Thinkpad X61s please

#1 Post by jkn » Mon Apr 17, 2017 5:54 am

Hi All
Recently my trusty old X61s died - I had foolishly left it powered up (via a docking station, and possibly with a fake "Lenovo" power supply) for a long period of time. When I returned it was totally dead. After a bit of investigation I have opened it up and discovered one chip that is undoubtably dead - see attached photos.

I am not sure that it is feasible for me to replace this chip (and of course it may not be the only fault) but I am pretty good with a soldering iron and am considering having a go. Can anyone help me identify the blown part?

The chip is an 8-way DIL small outline IC, situated on the underside of the motherboard near the dock connector. There are a few markings nearby but I am not certain if any refer to the actual chip.

if anyone can help me identify this chip (and perhaps even the fault that caused its demise) I would be very grateful. I am binning the suspect PSU FWIW!

http://images.jkn.webfactional.com/x61s ... chip_1.jpg

http://images.jkn.webfactional.com/x61s ... chip_2.jpg

The first image is a photo of the general area, and the second is a bit of a close-up for the frazzled chip

Thanks a lot
Jon N

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Re: Help Identify this blown chip on Thinkpad X61s please

#2 Post by RealBlackStuff » Mon Apr 17, 2017 6:57 am

That is chip U47, a MOSFET with P/N SI4425BDY-1-GP
The nearby Q43 is a MOSFET with P/N SI4435BDY-T1-1GP
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Re: Help Identify this blown chip on Thinkpad X61s please

#3 Post by jkn » Mon Apr 17, 2017 7:13 am

RealBlackStuff wrote:That is chip U47, a MOSFET with P/N SI4425BDY-1-GP
The nearby Q43 is a MOSFET with P/N SI4435BDY-T1-1GP
Wow, that was very quick, thank you!

Do you mention Q43 for comparison, or just for refernce? I wonder why one has the 'Q' prefix, and one has 'U'? That was partly why I wasn't convinced that it was U47 I was looking at.

Is this failure a well-known one? I am wondering how much hope I can put into being able to resurrect the laptop. I can get the mosfet via Farnell (in the UK, similar to Mouser etc.) but I wouldn't be surprised if the pads/traces are too vaporised.

Thanks again for the great start anyway!

Regards
Jon N

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Re: Help Identify this blown chip on Thinkpad X61s please

#4 Post by RealBlackStuff » Mon Apr 17, 2017 8:06 am

D=Diode
R=Resistor
C=Capacitor
J=Jack
Q=Questionable(?) :mrgreen:
U=Universal (?), used for many power-related chips

MOSFETs are the ones that blow if power is "overdone".
Can happen on any laptop.
Replacement might fix it, but check the neighbouring parts as well.

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Re: Help Identify this blown chip on Thinkpad X61s please

#5 Post by jkn » Mon Apr 17, 2017 12:37 pm

RealBlackStuff wrote:D=Diode
R=Resistor
C=Capacitor
J=Jack
Q=Questionable(?) :mrgreen:
U=Universal (?), used for many power-related chips
Heh - I like the 'Q' ;-). I am used to seeing that for discrete semiconductors.

Is there a parts list for the Motherboard that your info came from, or is this your 'accumulated knowledge'? I have the HMM but it doesn't go anything like as deep as individual components. I am just thinking about identifying the neighbouring parts you mention.

Thanks a lot

Jon N

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Re: Help Identify this blown chip on Thinkpad X61s please

#6 Post by rkawakami » Mon Apr 17, 2017 3:17 pm

RealBlackStuff wrote:D=Diode
R=Resistor
C=Capacitor
J=Jack
Q=Questionable(?) :mrgreen:
U=Universal (?), used for many power-related chips
Forgot:
F=Fuse (or F#&%$ part blew up again!)
L=Inductor
Y=Crystal
SW=Switch
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Re: Help Identify this blown chip on Thinkpad X61s please

#7 Post by RealBlackStuff » Mon Apr 17, 2017 3:36 pm

The details came from the X61 schematics, a.k.a. KS-3 Block Diagram
Google is your friend...

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Re: Help Identify this blown chip on Thinkpad X61s please

#8 Post by jkn » Mon Apr 17, 2017 5:00 pm

RealBlackStuff wrote:The details came from the X61 schematics, a.k.a. KS-3 Block Diagram
Google is your friend...
Got it, thank you. I have previously tried (and failed) to find schematics for other Thinkpads, and had assumed the same would be the case for the X61. I seem to have found something useful with your hints...

Thanks again, Jon N

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