I have a Dell Latitude C640 laptop. It shuts off all the time and can usually only get windows loaded and it’ll shut right off
Hi, I have a Dell Latitude C640. It shuts off all the time and can usually only get windows loaded and it’ll shut right off, then it will turn on and turn off right away at boot. I’m very familiar with taking these apart and when this first occurred I suspected a clogged cooling system. So I checked, and it was clean as a whistle… hmmmm…so I’ve been looking for anything out of the ordinary on the motherboard but everything is tight and looks clean. Even took the LCD apart to make sure there weren’t any loose connections. So if you could give me any insight on this it would be a great help! The only thing that “SOUNDS” suspicious to me, is that sometimes I can HEAR the power when I plug it in, a very faint high pitch ringing noise…. so then I figured well if its the plug technically it should still run fine off the battery, but it does the exact same thing. I’m also suspecting that maybe my fans aren’t running fast enough?? Or maybe I need some new thermal grease on the CPU??? HELP!!
Yeah, looks like an overheating problem. By the way, have you checked if the fan spins at all? May be it stuck and causing this high pitch noise?
I would probably remove the hard drive and boot the laptop from a Knoppix CD. Knoppix is a live Linux CD and it will boot your laptop to a Windows like environment. You don’t need the hard drive to boot the laptop with Knoppix, only the DVD/CD drive. If the laptop boots fine and doesn’t shutdown, then something is wrong with the hard drive or with the operating system on it.
Also I would test the memory module. You can run Memtest 86+ and see if the memory fails the test. It’s possible, that the memory works fine for a while when it’s cold, as soon as it warm up it fails. That’s why your laptop works fine for some time, and then just shuts down when you restart it. If the laptop doesn’t run long enough to finish up the memory test, then try to replace the memory if you can find any test module.
Of course, I would try to reseat all connectors inside the laptop. Any loose connection might cause this problem.
March 7th, 2010 at 4:26 pm
hi,
me again,
i fixed several c640 with replacing th u45 chip..
but now i don’t have a u45 chip anymore the fix another c640
lap..
but i have here 3 motherboards from toshiba , (sp6100, tecra9100)
is the u45 chip on these boards also?
if yes, where are they located?
and are there more maxim chips for 2,9 volts on a c640/c600/c610 board? or is it just one?
thanx a lot for any reply!!
frank
December 27th, 2009 at 6:48 am
i have a similar problem, i have a dell microsoft windows xp. i don’t know anything about laptops so.. when i press the on button the windows loading thing comes up and once its done it goes black, i think the screen might be broken but i’m not sure,i was wondering is there anything i can do before i go to a shop?
September 21st, 2009 at 7:55 am
The problem is the DC Jack, it is not working properly. Dell used faulty DC Jacks on the C640, and they have been known to eventually fail to receive the current needed to charge the battery. I’ve recently purchased a new one on ebay, I will now have to Desolder the old one and install and solder in a new Dc jack. I’ve purchased new cords and batteries to no avail, after much research and finding out that DC Jack Replacement is a service offered all over the net, I knew what the problem was.
Do a search on Yahoo: Dell latitude c640 dc jack repair (or copy and paste the links below..
http://search.yahoo.com/search?p=dell+latitude+c640+dc+jack+repair&ei=UTF-8&fr=moz2-ytff-ushdl
http://www.notebooksolutions.ca/zc/index.php?main_page=product_info&products_id=1875
September 6th, 2009 at 11:21 pm
My Dell C640 is not battery charging i was allrady change Battery and charger but problem is not resolved. Please provide salutation.
September 6th, 2009 at 9:37 am
l found out that usually when it switches off and on the problem will be the 3 power ic’s that work with the hissing noise from the inductors so it’s best you check those ic’s and replace them l’ll give you a picture later
August 16th, 2009 at 6:42 pm
I have the same problem with C640s. Can you tell me how the C640 senses the lcd/lid is closed? Is it possible that the sensing mechanism can fail causing these symptoms?
August 15th, 2009 at 8:00 am
thanx for the reply..
i just replaced the u45 with a c600 ic..
i shall see what happens..i ll put my lappy together with no
screws ect , just to see how long he will be in the air..
does anybody know where i can buy the u45 FM809SS3X or equivalent in europe or the benelux? without the horiible expensive shipping costs?
(newark asks 25 dollars for five ic’s)
thanx
August 12th, 2009 at 2:26 pm
VERY tardy update …
Changing out the U45 SMC successfully repaired my C640.
Kim
Previous posts in this thread: 94,95,97,100,101,104,106 … I think that’s all.
May 31st, 2009 at 2:53 pm
i want to put a resistor on the (bad)u45..
like the polish website..
they say this is a “kind of fix”
my question is:
is this a permanent fix or do i have to take the c640 apart
again after a while?
i also order the 2N2907 for this board..
is this 2N2907 a better solution?
gr frankie