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Laptop Motherboard Fan wont start


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#1 onlyprinzp

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Posted 09 March 2017 - 10:31 AM

Hello everybody,

 

I am new to this board and so I would like to ask a question, maybe somebody can help me.

 

The problem I am facing is that the fan on my motherboard of my laptop wont start. The strange thing is that first it was working. Then I switched it off and suddenly wont work anymore. ( the fan only ) More strange is that the laptop functions perfectly, just that it get heaten up badly due to the fan issue.

 

I took out the schematics of the board and found the fan control section shown below:

 

9bQIovg.jpg

 

When I measure the PIN1 of JP26 with a multimeter I only get about 0.26V instead of 5.0V, for the fan to work. 

 

The U26 chip shows the following readings:

 

PIN1 - about 5V

PIN2 - about 5V

PIN3 - about 0.26V

 

If there is somebody who could help a little would be much appreciated!

 

Thanks in advance!

 

The fan is not the issue, i hooked it up to 5V and spins like a charm.

 

PS: I have attached the whole MB schematics !

Attached Files


Edited by onlyprinzp, 09 March 2017 - 10:35 AM.


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#2 dc3

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Posted 09 March 2017 - 11:18 AM

The power adapter provides a single DV Voltage which the motherboard converts to the needed voltages, 3.3V, 5V, and 12V.  For this reason it is pretty clear that there is a problem with the motherboard.  Is this computer still under warranty?


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#3 onlyprinzp

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Posted 09 March 2017 - 11:25 AM

Hello thanks for the reply,

 

I have measured those voltages. All are good. It reaches 5V on the U26 Chip at PIN1 and PIN2 but gives out only 0.26V to the fan. This is the reason why the fan wont spin at all. I am trying to find the reason why this is happening. I changed the U26 chip with another one, but the problem still remains.



#4 dc3

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Posted 09 March 2017 - 11:44 AM

From the information that you posted the fan is not getting the 5V needed to the fan.  Obviously this is a problem with the motherboard.  I don't see how it could be anything else.  These boards a wave soldered, using the technique results in very very few cold solder joints, but there is always the possibility of one occurring.  If you have decent soldering skills you could try redoing the solder joint/s.  If you have problems getting the solder to flow you will need to add flux to the solder, or you could use a desoldering tool to remove the solder joint and then resolder it.  If this doesn't resolve the issue... take it to a good repair shop.  They will want to replace the motherboard.


Edited by dc3, 09 March 2017 - 11:45 AM.

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#5 onlyprinzp

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Posted 09 March 2017 - 11:49 AM

Ok thank you for your advice. One more question, I have measured with the multimeter the PIN3 of the U26 it shows the 0.26V, but gets the 5V from PIN1 and PIN2, is it possible that the VSET(PIN4) regulates the output voltage of PIN3 ?



#6 dc3

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Posted 09 March 2017 - 12:05 PM

Fans on laptops and notebooks regulate the voltage which regulates the RPM of the fan.  As the heat rises the RPM of the fan increases.  What ever means they are using to regulate the fan could have failed.
 
Please download CPUID's HWMonitor to view the voltages and temperatures.  Either make a screen shot of these readings or use the Snipping tool to create a image. 

 

You can post this image in your topic using the following method.

Just below the area where you write text in a post there is the Post button, to the right of this is More Reply Options.

Post2_zpsf05c0430.png

When you click on More Relpy Options  you will see Attach Files and Browse, click on Browse, this will open Pictures on your computer, click on the image you want to post, then click on Attach This File, then Add Reply.

attachment_zps9v6amtri.png

 


Edited by dc3, 09 March 2017 - 12:06 PM.

Family and loved ones will always be a priority in my daily life.  You never know when one will leave you.

 

 

 

 





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