x200s wont run off battery

[suodiss]

Hi this afternoon i had a perfectly working laptop with good 6h of battery time in 60 cycles battery.

But after pluging in (around 70percent charge) sleeping laptop to AC, ant taking it off 20 mins it wont start on battery. It will only do a high putch noise in the left upper corner near the went. It only starts on AC. If i unplug AC and leave the battery it emediately shuts. If i plug AC but dont plug it to the outlet ant try to run it of battery AC and Battery lights blink. THere was a smell of plastic when i first tried to turn it of battery. Did some sort of controller burned? What could have happened? Can it be fixed.

Ty for help..

[suodiss]

Today i dissasebled the laptop. Found the burnt part. Maybe anyone nows the exact part for replacement? T.Y.

PICTURE
http://www.part.lt/img/a23ffc3f4956d540 ... e3c209.jpg

[rkawakami]

It is a MOSFET. Additional information provided in my PM.

[suodiss]

I didn't belieave in my ability to solder, so i gave it to a guy who claimed he works at a laptop repair shop. He resoldered the chip, but the mobo didn't work.

I noticet he lost an inductor near the chip he needed to resolder. I connected the contact without the tiny resistor which is lost. Laptop works now properly. My question is what is the purpose of that inductor, and if it is very neccessary, or should i forget about it and just use the lappy.

Thanks.

I attach the scheme and photo of the mobo.

Schematics of x200s mobo http://www.datafilehost.com/d/81cfec3a

http://www.part.lt/img/c55faff006e23b78 ... c89d25.jpg

Admin edit: Fixed the link to the 1.8MB image.

[rkawakami]

Replied via PM but I'll also put this here for others to reference.

The part that you have circled (RT5) is a thermistor; a temperature-dependent resistor. The usual purpose for this type of part is for monitoring the system temperature and doing something when the temperature gets too cold or hot. Think of it as a fuse that is triggered by temperature and not by electrical current. This one happens to be a Murata PTC PRF15BB47QB. The resistance at room temperature (i.e., 25C) is 470 ohms. It rises to 4700 (4.7K) ohms at 115C. PTC means "positive temperature coefficient"; a fancy way of saying that the resistance increases when the temperature increases. The flip-side is an NTC or negative temperature coefficient version. That type of part will decrease in resistance when the temperature rises.

You say that you couldn't find the missing thermistor and simply solder bridged the contacts on the motherboard where the part used to be. This is equivalent to soldering a wire across a blown fuse. While the laptop may work for now, you have basically removed a part of the system that protects against excessive heat. If it were my motherboard, I would not use it until I found a proper replacement thermistor; one that has the same temperature/resistance performance as the original part. Since that thermistor was located next to the MOSFET that blew up, my guess is that it is supposed to monitor the temperature in that area of the motherboard. If it is exposed to excessive heat, then it should shut the system down. However, as with most types of fuses, the semiconductor being protected is usually faster at blowing up than the fuse.

A replacement thermistor can be tested before installing it on the motherboard. Measure the resistance at room temp. It should be near 470 ohms. Heat it up with a hair dryer / heat gun or hold a hot soldering iron near the part (don't actually touch it). Measure the resistance again. It should have increased to near 4700 ohms assuming that the temperature near the thermistor is around 115C.

ref: http://www.murata.com/products/design_s ... /spec.html

[Brunoce]

I looks like I have had the same problem.
Would you pass on the information. The picture are no longer available.
Thanks a lot!
Bruno

[rkawakami]

@Brunoce: Welcome to thinkpads.com!

I did not keep any of the images that suodiss posted. You might want to try contacting this user via Private Message (PM).

[Brunoce]

Thank you for your welcome message. I will surely do.
Thanks
Bruno