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.
August 7th, 2008 at 12:06 pm
I fixed it guys. I stored this computer on the shelf for a year and now thought I would try to fix it. I did it…
….All I did was remove the back door that is there for adding more RAM. On the rubber strips that are on the door I folded up a piece of paper and taped it on the strips (making it thicker and thus press on the motherboard harder) and now the machine has been running an application for over three hours.
see this http://img180.imageshack.us/img180/2716/spa0057uo7.jpg and this http://img263.imageshack.us/img263/5717/spa0054za5.jpg for a (bad) image of what I did
August 2nd, 2008 at 10:47 am
Those of you that mention the fan “problem.” From what you mention it doesnt sound like a problem at all. My laptop works perfectly, and when I power up my laptop my fan doesn’t spin. It shouldn’t have to. My fan only starts spinning when the cpu starts to get warm. The same EXACT thing would happen if you were to take off the radiator fan on a car. You guys say that the fan starts spinning when you take off the fan. Of course, because since you have the fan off, the cpu is getting hotter quickly, therefore the fan kicks on.
Power up the laptop with the fan in place, go into Windows, and try doing something cpu intensive and see if it spins. Install a cpu temp monitor program (such as I8kfanGUI)and monitor the cpu temps. I always keep it open on my taskbar next to the clock. If it starts hitting 60 degrees celcius and the fan is still not spinning slowly, then yes you do have a problem.
I understand that some laptops upon first turning it on, does a FULL fan speed test, but of the 3 C640′s I have, none do that. Only my Toshiba and Gateway do it. I also own a Dell C610 and that one also doesn’t do the full speed fan test upon powering up the laptop.
July 30th, 2008 at 5:22 am
I have the same problem as Jerry.
My D640 had been running fine but the last time I used it the battery was powering the laptop, even though the AC cord was plugged into it. I noticed the green light on the power transformer was not lit and suspected a bad unit. I replaced it and same thing…as soon as I pluged the AC cord into the laptop the green light on the AC transformer went out. The d640 runs fine on battery… Does anybody know how to correct this AC power issue?
GerryP
Jerry Says:
May 28th, 2007 at 7:20 am
I have a similar issue with my Dell C640, but slightly different. My laptop works fine on Battery power but it will not charge or run on AC power. I have dis-assembled the laptop, cleaned the board with canned air(attached my electro static discharge cable too). I re-assembled the laptop and plugged it in, it still does not recognize the Power Supply. I have purchased 3 brand new power supplies, and tested them on another Dell laptop( I love Dell). I still cannot get the laptop to run or charge on AC. Can anyone help me out here? Thanks.
Jerry
aka Vampnite69
July 24th, 2008 at 5:02 pm
My ABS Mayhem G3 has been doing something similar. I fixed one problem where my CMOS battery wasn’t making contact with another piece, so that fixed the weird freezing up and flickering, but now my laptop won’t run on AC power. It works on batter power well enough, just a little slower and not nearly as long. It charges normally, too. It runs on AC power in bios and in safe mode, and I’ve reinstalled Windows XP pro 3 times so far, so I think it might be my hard drive. I would just like to know if there is anything I can do with Windows to get it to like the big plug in the wall. If they could make up and just be friends then we could all get along just fine. (whoa, those hippies are starting to get me) I tried looking at msconfig, but I don’t really understand most of it. I would try using a different hard drive if I had one; I might have to sooner or later. If you have any ideas, please let me know. Thanks!
July 18th, 2008 at 9:55 am
I have an compaq 2500 laptop, everytime i try to install windows updates or do any high activity my monitor will go black with a faint image and the power light is still on and so is the battery light but the hard drive light shuts off and the computer is locked up. If i hook it up to a external monitor it works fine.
July 16th, 2008 at 6:28 pm
If 4 of us on this site alone have the same symptoms, it was probably a significant defect with the c640′s and perhaps someone out there found a fix or workaround. One possibility that might cut the fan off when tightening down the heat sink is that the added pressure might be causing an short or open circuit in one or more of the socket to board connections. None of my module pins looked bent, and I don’t have a spare, but I did reseat it several times as a test. I suppose we could prevent overheating by using another 5V power source for the fan, but then it would run at full power all of the time and kill the battery in short order- but I guess that would at least retire the laptop to a desktop instead of leaving it for dead.
July 15th, 2008 at 11:01 am
I actually tested my laptop and noticed that it has the same issue that Ben (July 14th, 2008 at 8:14 am) is having. There’s something with putting that screw in that doesn’t make any sense to me.
July 14th, 2008 at 8:14 am
I have the same problem as Jimbo. With the heat sink on the fan will not come on, but if you take it off or even unscrew it it will come on. You can even unscrew it with it running and watch it come on and then screw it down and watch it turn off. IF anyone has a fix let me know please. It is driving me crazy.
July 10th, 2008 at 4:35 pm
I have a c640 with identical problem as Conket described on 5/1/08. With heat sink attached fan does not come on (even at startup). Remove it and fan works. Does not come on even if heat sink is in place but not screwed down. Must be a short, but don’t see anything obvious. I could test likely components but it overheats too quickly. Perhaps supply external air to keep pc going, and then poke around for for shorts. Any suggestions would be most appreciated.
July 8th, 2008 at 11:28 pm
SM,
Apparently, the CMOS battery is bad and has to be replaced.
Clean the heatsink with compressed air, I think it’s clogged with dust.
July 8th, 2008 at 4:53 am
I use my C640 Dell laptop to try cloths – while i am using it. it gets very hot at the bottom
!
laptop’s bottom
and every time i power on – it asks me to go to setup with a message that setup is wrong.
Whats wrong with this fellow?
Does a laptop uses its big battery to provide power to CMOS settings? (like the small penny size batteries do for the motherboard of a pc?)
another thing i have noticed that, if I switch off the power – sometimes the battery power won’t work, it just switches off the laptop.
any help appreciated.
July 2nd, 2008 at 4:58 am
Hi
Success
Problem was not MIC5236 but transistor further down the line. Look For U45 short circuit 70mm due north.
July 2nd, 2008 at 3:12 am
Hi
The real number is MIC5236-3.3BM manufactured by Micrel.
I am going to remove chip and place it in test circuit.
Datasheet is available.I suspect a short circuit downstream. Anyone got schamatic for C640
July 2nd, 2008 at 2:49 am
Hi
I have same problem with voltage regulator chip and am trying to salvage one from old boards that a dealer gave me. Chip sits under VGA socket. Wish I could find new
June 20th, 2008 at 3:13 pm
Guy’s I’ve solved the problem on the DEll C640. After hours and hours of research on the net I concluded to open up the box of electronic and do some investigating.
I found the problem There is an electronic component called u25 (It’s number is M5236 -3.3BM) it’s a voltage regulator IC manufactured by mitsubishi electric. It is used in tandem with another adjacent to it (on the under-side of the motherboard).
The chip gets hot and burns out causing a short circuit. I have managed to find a replacement chip on the net (ebay of all places) and I’m waiting to fit it.
Now be careful, use a solder braid. don’t use a wacky desoldering tool!!! because you’ll burn out the pcb and the copper tracks will lift off.
The braid sucks up all the solder leaving a very thin layer to tack the component. Next, get a tooth pick ot fine jewellers screw driver and prise-up each leg 1 by one.
When it comes of, replace it with the new chip. In all honesty, It might cook again until I find the fet or transister that is causing this overload.
I’ll let you guy’s know how I get on (today is 21/6/08) thanks..any questions email me on sabras@orange.net
May 23rd, 2008 at 5:23 am
I had intermittent shutdown and RAM problems for my Dell C640 similar to those reported in this thread. Adding pressure to the RAM using some thin slices of a foam block has resolved the problem. Thanks!
May 14th, 2008 at 9:26 pm
This is such an awsome thread. I just got my C640 last week and everything runs perfect except for a few things. It came with a 512mb stick installed in jdim2 which seemed odd. I added a 256 stick to jdim1 and got memory read errors. Ok so I assumed the ram I had laying around was bad. A few days later I moved my 512 stick to jdim1 and id either get caps blinking or memory errors. So now I knew it wasn’t the ram that was bad and said “ohh well, I’ll just live with 2ghz, 160 HDD and 512mb ram” untill I read this thread. I tried the pressure on ram method and NOW JDIM1 WORKS!!!! I’m typing this message on the c640 by the way
The second weird thing is, not a problem but just a weird thing. Someone else mentioned this earlier in this post. When I go to turn on the laptop at any time, 95% if the time it won’t turn on the first time I press the power button. Instead the battery light blinks “Amber Green Green Green Amber” but as soon as I hit power again, it powers right up. The battery I was told by the seller is brand spanking new and I can squeeze over 4 hours out of this battery if not doing anything intensive. The battery charges just fine and it discharges just fine. I just don’t understand the blinky thingy and why it does it.
Other than that, the laptop is perfect and in new condition. I just ordered a Intel Wireless b/g mini-pci card for dells since the stock 1150 series I have sucks in range, speed, and encryption support. It can only do WEP..eww.. Anyway, any thoughts? And I am another one to confirm that the “pressure on ram” method works!!!
May 5th, 2008 at 2:21 pm
tusja,
If only some of the keys stopped working then most likely you have a keyboard related problem. You’ll have to replace the keyboard OR use the laptop with an external USB keyboard.
This also could be related to the keyboard controller failure, witch means you’ll have to replace the whole motherboard, but it’s not a common failure. You cannot tell witch one the keyboard or the motherboard is causing the problem until you test the laptop with a known good keyboard.
May 5th, 2008 at 2:06 pm
Hi,my C640 has a problem with some keynotes: b,n and the spacebar. It’s so uneasy to write..Could someone please help me…Or tell me whether it can be solved or not?
thankss
May 1st, 2008 at 6:47 am
Hi,
My c640 is having problem with shutdown and restart, after that that the time it get up is shorter and stop. I narrowed it to the fan, when you power it up the fan is not working at all, or after that. I took everything off bare, right before I take the fan out I thought let try to power it up one last time, the fan is working. I said to myself that is weird, so I put the heat sink back. Power it up, the fan is not working. Removed the heat sink, power it up, the fan works. Could someone tell me what kind the problem I have? Is it circuit on the mb bad?
Thank in advance!
April 18th, 2008 at 12:23 pm
Hi!
I have a problem with Dell Latitude C640 as well. After reading this whole forum I believe that the thing happening to the laptop is the pre-phase of overheating problem.
The problem looks as follows:
When I load the processor heavily for a longer period of time (around 10 minutes) the fan starts to work at maximum speed, emits a lot of noise and that is normal. The problem is that when the processor is idling after doing some effort, the fan still rotates at the max speed until I shut down the system. The Fn-z combination slows it down only for 20 seconds.
The HDD temperature is between 40-56C and the motherboard sensor shows no more than 52C.
The worst thing is that once the fan starts to spin at max – the computer’s performance goes down dramatically. After rebooting everything is fine… until the fan spins up…
I would be greatful for any advice.
Greetings!
April 8th, 2008 at 9:26 pm
I have a few problems with my C640 too but none of your problems.
1)Battery won’t charge at all and they are known good batteries. Whenever I insert a battery in the laptop it just shuts off. When a battery is in it and try to start it, it won’t start. Charge light stays on for about 5 seconds. The CD-ROM works fine in either port though so it just shuts off when a battery is inserted. Used 3 different good power blocks.
2)Power port has loose connection as whenever I slightly touch the cord it just shuts off. Is it possible to resolder or should a laptop repair guy so it? Are the refurbished c640 motherboards on ebay as close to new I can get without spending $400 for one from dell?
March 27th, 2008 at 1:00 am
i have a dell c640 thats does not charge the battery but runs fine from both the bios and the windows…please can any one tell me the solution to this..thanx
March 7th, 2008 at 1:41 am
i have a c640….the small fan in the rear never comes on and the laptop runs very hot. Ive never experience the random shutdowns discussed here but can seem to make that small fan work. i did disassemble and check and there is not binding in the fan. is there a “switch” to enable that fan. i installed the fan controller and it only has setting for the large fan on the right rear.
Thank you,
rob
February 29th, 2008 at 2:16 pm
I realize that if I adjust the brightness of the screen and set it to the dullest and turn the system on it stays on.. however if I was to turn up the brightness when its been operating it wound shut off..What could this mean?
February 27th, 2008 at 8:01 pm
It’s possible that you have a problem with the inverter board.
You are correct.. The screen has a faint image, hence the screen is very dark.Is the inverter board integrated or it can be purchased and replace? I pulled the system apart and reassembled it…The problem is still occurring.
February 27th, 2008 at 8:00 pm
It’s possible that you have a problem with the inverter board.
You are correct.. The screen has a faint image, hence the screen is very dark.Is the inverter board integrated or it can be purchased? I pulled the system apart and reassembled it…The problem is still occurring.
February 24th, 2008 at 10:31 am
tango,
Take a closer look at the screen when it’s blank. Is it really blank or just very dark and you still can see a dim image? It’s possible that you have a problem with the inverter board.
February 21st, 2008 at 2:48 pm
I also have a c640. I noticed that during the boot up process it stayed on 4 a few seconds before the screen goes blank. After waiting about 5 seconds of the blank screen I hold (fn+f5)and the screen blinks. I would then go through a series of (fn+f5) then (fn+esc)for the screen to remain on.
February 19th, 2008 at 11:06 am
I have the same sudden shut down symptom at my C640 laptop, i found it doenst matter what bay the ram is in, it does nt like both sticks. mine works perfect when only one stick is in, they are 2 matching 512mb that worked fine before now.