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.
October 14th, 2008 at 2:43 pm
Hi,
I am going to apply the grease on the heat sink but I do not know exactly where to apply it. Should I apply it on the bottom of the whole heat sink or just over the rectanglular area in the middle which is placed on the CPU. One more thing I don’t understand while cleaning the heatsink is that do I have to completely remove the black layer below the heatsink or just wipe the grease in the rectangular area in the middle? If anyone has an answer with the picture, it would be much helpful for me.
Thanks in advance.
October 14th, 2008 at 8:27 am
I have a Dell C640 that will not run for long on ac only, generally not complete boot up, with the battery in place and no ac it appears to work ok, with battery and ac it will run but the LCD screen intermittantly darkens or goes blank the back to normal brightness. When I have the ‘power meter’ displayed it shows ac much of the time but switching to battery and back to ac. I suspect a dry joint on the ac input plug, wiggling the adapter cable has no effect, and have followed the Dell instructions as far as removing the system board, however the actual mother board has metal plates (covers) top and bottom and as far as I can see both need to be removed to get at the plug’s solder terminals.
There appear to be many screws and nuts to remove and some plates seem spot welded.
Is there any guide as to which to remove and what to leave alone? From the many entries above working at component level several people have dismantled that far.
Any advice gratefully received.
regards Mike
October 9th, 2008 at 8:18 pm
Hi. Big respect to the chaps who sorted out the u45 problem.
Can I run this little “feature” of my pair of c640′s past you all and ask for comments? I used to get surplus latitudes from a well known software company, by way of a clearance, and kitted out my G/F with a pair of c610′s some time ago, runnning at just over a Ghz.
When I got some c640′s running 2.2Ghz processors I expected a huge speed increase.. Not only didn’t I get that, but I started getting complaints until I eventually reinstated her old laptops. I’ve been using this c640 for a while now, and most times it’s fine, but every so often it just slows to a crawl for no discernable reason. I got a mate (who should know, he used to fix laptops all day long) says that p4′s are just plain rubbish compared to p3′s. Anyone have a similar experience to me? Cheers, Steve C.
October 6th, 2008 at 10:02 am
I would like to thank all those who have been involved in the diagnosis of this problem which I know would have been many hours of work, I have replace U45 transistor and the laptop is working great.
Regards
Phil K
October 4th, 2008 at 10:40 am
The U45 transistor is FJX4010R from Fairchild. It’s very similar to 2N2907 with a little diference, the 10k resistor. I put this on my DELL and it works fine. Probe this if you don’t have the same transistor. Don’t forget the resistor.
October 3rd, 2008 at 9:43 pm
Follow up of my post on July 15th, 2008 at 11:01 am:
I went ahead and ordered the part from Newark as stated above. I just changed the thing and put it back together and VOILA!!! This thing has been up for about a half hour (WHICH IS WAY LONGER THAN EVER BEFORE) and still going strong.
For me, the actual replacing of the part wasn’t too difficult, it was actually taking the thing apart. You pretty much have to take the laptop apart COMPLETELY! Even with the service manual it was kind of a pain. Anyway, this fix works well. THANK YOU AGAIN!!!
September 30th, 2008 at 4:34 pm
Hi, I’ve been having a similar problem with my mom’s c640 but it will freeze in the bios and when I boot it up the Dell logo is about 1/4 it’s normal size.
My mom has gotten a replacement after we decided that it wasn’t worth the time fixing but about a week ago I took another look. I asked one of my Linux buddy’s and he told me to unplug the bios battery but to no avail. I don’t know what’s wrong with it but I put new thermal grease on it and that did nothing. After I read this thread (btw very interesting) I think it has to be something with the mobo.
ps
I have been able to boot into windows but it wont boot to livecd.
September 28th, 2008 at 10:57 am
I,also, would like to thank Madmax, Rupert and John for all the work on this.
I had the shutdown problem. I saw this thread, ordered 5ea of the Fairchild IC’s (under $2.50 delivered).
I disassembled my motherboard, took one look at the component. No way I have that kind of skill but I have a telephone. Made 2 calls and found a computer repair person who said he’d do it. He charged $25.00!!! What a deal. I’m writing this on my C640 which has been on, continuously for 36 hours now. All for less than 28 bucks!!! I cannot thank you enough!!!
Kevin
September 25th, 2008 at 6:52 am
Hi, I am from Argentina and I have the same problem. I found the datasheet for the U45 and it is a simple transistor PNP with an 10k resistor in the base. I don’t have a replacement for that transistor so I put a 2N2907 with a 10k resistor in the base. Now the PC works great and don’t shutdown any more so thanks for the help and I hope this help. Sorry my english. Saludos.
September 19th, 2008 at 10:12 pm
Hi,
yesterday I picked up a not working DELL C640. No power up with a full charged battery and if I plug in the power adaptor the led in the power adaptor goes out. Maybe a short circuit??
In the night I dismantle the complete notebook and found U45 on the motherboard.
Today I try to replace it with a diode. Report follows
Touch wood!
regards
Thomas (Germany)
September 17th, 2008 at 4:10 am
Hi All,
I don’t think that it is demanded to build in the Maxim IC. There are a lot of similar parts on the market. It is simply a 3V3 voltage supervisory IC that has a typical theshold of 2.93V. For Europe the easiest way would be RS Components having TI ICs on stock packed to 10 for about 3 Euros. For US I think digikey would be the Source of choice.
Regards
Max
September 14th, 2008 at 2:32 pm
Hi all,
Great thread.
I’ve been given a C640 to repair and upgrade. After upgrading the RAM, to my horror, I started having random reboot problems.
After reading this thread, I can confirm that the putting several bits of business card on top of the RAM to apply pressure works
Cheers,
Binky
September 13th, 2008 at 8:35 am
Thanks to Madmax, rupert and John for all the work on this; it can rather hard (to say the least) to figure out an intermittent failure like this. Maybe I can fix my brothers Latitude now. Methinks I’m gonna need a darn small soldering iron tip.
John, I guess you ordered the Fairchild because it was a) available as a compatible part (active low reset at 2.93V threshold) and b) a lot cheaper even though it used twice the supply current (2uA – don’t think that’ll be an issue).
I don’t think I’ll be able to source the Maxim chip here in Ireland anyway (assuming they have the 2.93V version out of the 21 versions of that chip) so I’ll go look for that fairchild now!
Thanks guys…
September 12th, 2008 at 9:21 am
John thank you for the info!
Can you put a picture of the setup you made.
Thanks.
September 12th, 2008 at 9:03 am
Many thanks for the info, John!
For those of you wondering about the actual location of U45 on the mobo, here is a pic:
http://i7.photobucket.com/albums/y285/Jungesblut/Stuff/U45.jpg
It is the little 3-contact IC between the “large” PCIbus & SMSC ICs.
September 11th, 2008 at 7:38 pm
The part I actually ordered is a Fairchild FM809SS3X…If you look at the datasheet this has a reset threshold of 2.93V. The part is $.42 each so I ordered 7 of these as spares and the total was less than $9. The URL is….http://www.newark.com/
The part is in South Carolina. What I did was run 2 wires from the solder tabs to locate the part between the memory so I would not have to dismantle if this goes out again. The ground I used a spot on the chassis near the shield for the left leg. The Newark part # is 58K1509…I put this in today and works fine. Hope this helps others.
September 6th, 2008 at 6:23 am
John,
Once you find a source that will sell QTY: 1 or 2 or 3 of the part upon which you decide, would you please share the details with us?
Thanks!
September 5th, 2008 at 8:33 pm
Thanks MadMax…I was almost 100% sure that was a reset for one of the microprcessor in one of the chips. With the IC out of the circuit the unit would not come on but momentary touching with the diode across the in and out would allow the unit to run. Once it was cut off this had to be done again so the temp fix I did was to leave the diode in the circuit. Reset circuits leave the voltage their so I figured it did no harm to leave the diode. I have operated a tv repair service for over 26 years so I have dealt a lot with having to redesign and make circuits work. This is great knowing what the IC actually is so I can replace it properly. Looking this up it is a very low current device @1ua. I think I will try to put something bigger in their so it will last. I searched and called numerous dell motherboard repair centers and none of them went that intense into board repair. This forum solved the problem and I appreciate the time saving advice. Thanks again to all.
September 2nd, 2008 at 4:23 am
Hello John,
I found on an working motherboard the U45 replaced with a different marking code FCAA which means Maxim MAX6326 CPU reset IC with 2.93V. I hope this will help.
Regards
Max
September 1st, 2008 at 6:53 pm
FWIW, after giving up completely on my laptop ever managing to boot-up with either the PA-6 or PA-9 power supply, I decided to try a lower wattage PA-2 unit (I figured that it might be easier on whatever PS component is flaking) … and I have had quite a bit of success, although once the C640 cops an attitude(about every other day), neither the battery nor the PA-2 succeeds.
September 1st, 2008 at 9:47 am
Thanks for the tip longstand, but I have tried that several times, now, and my C640 still still treats me to Sudden Cutoffs.
Hopefully, it will work for some others, though.
August 30th, 2008 at 2:17 pm
for all with the C640 SHUT OFF PROBLEM try this….
when it starts to boot hold the function key (fn) at the bottom left of the keys beside the lett alt key and press the down arrow a couple times. (fn+down arrow)
For the more technical persons press f2 after turning on the system while it boots. follow the instructions to say press (alt+P) to change the pages till you reach the brightness settings when power is plugged in and when on battery. adjust and see what happens!!!!
August 27th, 2008 at 7:27 pm
Another victim of the c640 Caps Lock flashes 10 times. I inhered the problem from someone how did not want it any more. I tried everything suggested and finally the answer. The memory does not seat right in the notebook. Cleaning the contacts did not work. I finally resolve it by adding constant pressure to the ram chips by using the spongy foam and double-sided sticky tape to the bottom access lid.
Some pics that might help.
http://img527.imageshack.us/img527/2391/img0963jq9.jpg
http://img527.imageshack.us/img527/3066/presentation1bu4.jpg
August 26th, 2008 at 5:37 am
Yes, before posting I read all of the posts, especially Daljits’, Rupert’s and yours, with great interest.
I, like you (and probably many others), am hoping that someone will be able give us an ID on the U45 part so that we can source a replacement and then change it out.
That failing, if your Diode Workaround continues to work, hopefully you will be able to provide more details to those of us that would like to repair our C640s.
Currently, this is not a major issue for me since I have several other systems that I may use … but I would like to get it properly repaired, eventually, and thereby possess the knowledge & experience JIC my sister’s “new” laptop starts exhibiting like behavior.
To you, Daljits and Rupert, THANK YOU for taking the time to share your discoveries with us!
August 25th, 2008 at 7:56 pm
Read my post above about U45. This is a small IC that looks like a 3 legged transistor. All of the posts above about pushing on board near memory are all related to the U45. Resistance would change when either pushing or freeze spraying the part. When AC is used the regulator is always on supplying 3.3V to U45. When battery is used voltage is on U45 only when on. This is why the regulator has a chance to cool down when AC is removed with the battery still installed. If the battery always works and the AC doesn’t then the AC power input posts probably have a cold solder joint. I have been unable to find out what that part U45 is from anybody. I got mine to work by removing U45 and putting a diode across the in and out and it has worked flawlessley for hours at a time with no shutdown. If anyone knows what that part actually is please let me know. Left side is ground, top 3.3V and right 2.9V. Taking it all apart is a pain. Hope this helps others.
August 24th, 2008 at 10:39 am
“I will try the addtnl-pressure-on-the-SO-DIMMS trick …”
Goodness! In my case THAT turned out to be a Bad Idea.
I cut one of my old business card in thirds, lengthwise, and, after trimming them to length, installed them under the access panel over the RAM sockets. I replaced the panel, tightened the captive screws and installed the center keyboard screw.
The system cutoff in mid-BOOT and would not start. I removed the center keyboard screw (which proved itself to be an Item Of Interest awhile ago in my troubleshooting) and the system almost got into XP before cutting off. It was behaving like it does on AC power even though it was on battery power.
I removed the pieces of cardstock, replaced the panel but not the KB screw and the C640 still presented with the No Start syndrome (even after removing & replacing the battery) …
… so I pulled the PCMCIA covers and directed a fan-blown steam of air into that area to cool off the components in the AC power supply area.
That was about an hour ago and now my laptop is back to where it was, running fine on battery power.
Apparently, my mobo does not like to be flexed like that … and I will have to look closer at that center KB screw.
BTW, one thing that I failed to mention in my initial post is that my BIOS is version A10 and has been since 2004(?).
August 24th, 2008 at 8:12 am
VERY interesting & informative thread!
My 2GHz C640 started flaking on me about a month ago … the Time/Date problem along with the Sudden Cutoffs followed by No Starts.
It has lived most of its life in a C/Dock getting turned on, primarily, for file synchro, OS updates and backups.
My month-long testing has indicated to me that the issue is directly related to the AC-to-DC circuitry on the mobo.
My C640 runs fine on battery and the mobo circuitry charges my batteries while the unit is off and plugged into a PA-6 alone or thru a C/Port or C/Dock (PA-9).
My C640 does not operate reliably for any length of time on AC … and the way(s) that it fails after the initial abrupt cutoff, strongly suggest that heat is a factor.
When I started this troubleshooting journey, I installed SpeedFan and was SHOCKED at the temperatures inside the laptop and the fact that the laptop’s fans were not kicked into HIGH because of it. I quickly searched the web, discovered I8KFANGUI and have been using it ever since … with the fans forced to highspeed.
Also, during that period (first thing, actually) I replaced the CMOS Battery Pack and, while I was rooting around in there, cleaned up the primary fan + path and the heatsink … and upgraded the CPU to 2.4GHz.
The two 512MB SO-DIMMs are also new.
I will try the addtnl-pressure-on-the-SO-DIMMS trick, but I seriously doubt that this will solve the issue with my C640. In my case, everything seems to point to one or more mobo AC power supply components having become heat-sensitive and flaky.
I am hoping that someone will be able to naildown the culprit and post about it so that I(we) can changeout the one or two board components and cure our laptops’ ilness.
Another reason that I am concerned about this issue is that I recently bought a partially stripped C640 and have been rebuilding it into a fully functioning laptop for my sister & her family (as a surprise … I have accumulated a lot of C-series accessories/components over the years).
August 15th, 2008 at 8:17 pm
OK – a number of us appear to have a slightly differnt problem than most. The c640 runs perfectly off of a charged battery, but the laptop doesn’t get any power from a known good ac adapter. Would it be worth the time and money to have a pro put a new power inlet in or is it more likely a problem on the motherboard?
August 11th, 2008 at 4:00 pm
I had a c840 that would freeze after about 10 minutes even with the fans on manaul control set to fast. After that it would not show the dell start up screen and would shut down. It would need to cool down for an hour or so to get it going. I dismantled it and put it back together with cleaned out fans and heatsink, more thermal grease etc. It worked fine for about an hour and then the same thing. I tried the taking the battery out, removing the power and holding the button for 10 seconds which would allow it to post but it would lock up soon after (2 minutes or less). So I tried the ram. Already I had only one slot working as the other does not recognise any ram that I put in it. I ran the memory testing software from a linux distro which crashed. Since swapping the ram (from 512mb to 256mb) I have had no crashes and the mem tester ran for an hour ok with no problems. I will now go and purchase an other 512mb ram stick to replace my 256mb as it is a bit slow and makes games laggy. I hope this helps others.
cheers
August 9th, 2008 at 8:45 pm
Rupert…..Thanks for saving me some time on troubleshooting the C640 with shutdown problem. The U45 was shorted to 60 ohms and freeze spray would make the unit work. The only number on the part is S60. Do you have a part number or know what it is? This is an IC and not a transistor and I suspect it is a regulator but not sure. Any help appreciated and thanks again for the time saving tip. Please leave comment here or email me ….ethion85485@mypacks.net…..Thanks again