Dell Latitude C640 dead

[nbanti]

hello. please help me on this. I have dead dell latitude C640. when i power on it, it is power on just for only 2 seconds. then is gos off. please tel me what can i do.. what i have to check. please response me please.........

[dood]

Re: Dell Latitude C640 dead

Try pulling the memory SODIMMS one at a time and see if it boots up with only one or the other socket populated. I've seen these laptops drop a memory channel lots of times...

[nbanti]

Re: Dell Latitude C640 dead

It is power on just for 2-3 Seconds. After that it gos power off. I can't find any physical burns. Please help me... What i have to check.. I am not a genius in laptop repairing.. Please help me on where to start checking this laptop. Please

[gabik111]

Re: Dell Latitude C640 dead

Common problem in that series. Remove laptop apart , find U45 (MAX6326 - 3pin - looks like transistor) that is located near BIOS chip and RAM slots. Unsolder and discard this IC. Short pin 2 and 3 like on the picture attached. Put everything together.

[Th3_uN1Qu3]

Re: Dell Latitude C640 dead

I don't know why they even make these crappy ICs if the computers start fine without them. Seen them failing before.

[gabik111]

Re: Dell Latitude C640 dead

Propably to kill laptop earlier. Then costumer will buy new one... 10% or less can repair that . Remain 90% will go to the sotre. End of story

[nbanti]

Re: Dell Latitude C640 dead

Thank you for the reply..

But it is not working after i have done your method. I have attached a image. All the marked items are showing short circuit when i checked using multimeter.
What can i do sir? Please reply me soon.

[Th3_uN1Qu3]

Re: Dell Latitude C640 dead

It's normal for some caps to show short circuit - it depends what they're attached to. If you lift them you'll see that they are fine. If those are the caps in the CPU area, removing the CPU will clear the short. This is normal behavior and the CPU is fine.

Check the mosfets in all power supplies. CPU, chipset, and so on.

[nbanti]

Re: Dell Latitude C640 dead

Dear..

I am not a genius in laptop repairing. I am just trying to get some experience. Can you please tell me which part is Mosfets. Pleas... Help me...

[gabik111]

Re: Dell Latitude C640 dead

Mosfets in power line looks like 8 pin IC (SOT8 ). Visible 2 of them on the picture attached by me (not actually those ).

[nbanti]

Re: Dell Latitude C640 dead

Thanks all of you Very much for yours help.

[starmaxpc]

Re: Dell Latitude C640 dead

Common problem in that series. Remove laptop apart , find U45 (MAX6326 - 3pin - looks like transistor) that is located near BIOS chip and RAM slots. Unsolder and discard this IC. Short pin 2 and 3 like on the picture attached. Put everything together.

Stand up so i can hug you!!! i have a dell c640 p4 laptop also with the same problem and did what u suggested only i didnt use the wire as pictured i only jumped the connection with solder at it is now working!! cant believe that removing a part makes something work?? any idea what that ic does and why it would disable the laptop and removed from board enables it??

Thanks

[Th3_uN1Qu3]

Re: Dell Latitude C640 dead

If you had read the datasheet of MAX6326 you would have understood why. That little IC is responsible for keeping the system powered down if the supply voltage isn't correct. Supposedly, to reduce the likelihood of smoke pouring out. It just sounds like planned obsolescence to me, especially since i've seen several reports of those ICs failing without anything else being wrong.

[Biancocf]

Re: Dell Latitude C640 dead

hello , i have a dell XPS 1330 pp25l and my U45 is a bit different, it have 8 pins , 2 pins each side and seems to have a micro small black resistor with 2.5ohm in one side, but i think it's too low value to a small resistor , can somebody check this value to me? i will take a pic later, thank's!!

[Biancocf]

Re: Dell Latitude C640 dead

Thank you for the reply..

But it is not working after i have done your method. I have attached a image. All the marked items are showing short circuit when i checked using multimeter.
What can i do sir? Please reply me soon.

i found a dell with the same issue , short in ceramic capacitors, all caps are shorted, this is very difficult to find the right one , but just one are bad making the mobo fail to everything , i fix this removing one by one starting from the power plug , after 4 caps i found one shorted and test the mobo without it and it work's perfectly , but weeks later another one cap shorted again , i change all caps and now it's ok

[alibisma]

Re: Dell Latitude C640 dead

hi guys i got the same problem dell inspiron 640m after 3 sec its turnd off i change ram and processer but sitll not thing plz help me out??????/

[Charles8803]

Re: Dell Latitude C640 dead

Common problem in that series. Remove laptop apart , find U45 (MAX6326 - 3pin - looks like transistor) that is located near BIOS chip and RAM slots. Unsolder and discard this IC. Short pin 2 and 3 like on the picture attached. Put everything together.

I replaced U45 in my Dell C640 and it worked quite well for a couple of years. Then died again. I presume that U45 is bad once more. What, if any, are the potential negative consequences of shorting the pins (I presume that U45 serves a useful purpose)?

TIA...

[dell_fixer]

Re: Dell Latitude C640 dead

Common problem in that series. Remove laptop apart , find U45 (MAX6326 - 3pin - looks like transistor) that is located near BIOS chip and RAM slots. Unsolder and discard this IC. Short pin 2 and 3 like on the picture attached. Put everything together.

Very old thread, but for anyone else looking at why their C640 has died, this is it! I removed U45 and placed a jumper across it as per instructions and my once dead C640 is running great again. Thanks to original poster for this info!