My Dell D800 laptop stop working.

When I plug the ac-adapter the power light goes off on the adapter. It is obvious short on the motherboard. I did took it apart and look for some problem around DC-jack, but I don't think the problem is there. All the accessories are off . It is only mobo now by it self and does same thing. Anybody knows where I should look for the short. Which chip or diode it could be? I heard it is very common problem with D800 and D600 models. Since I am pretty good with soldering I think, and it is my hobby as well I would like to repair the mobo my self instead replace. Definitely would be much cheaper as well.

Thanks in advance for any input on this matter.

Some laptops have a separate internal DC converter, and some DC converters are part of the motherboard. If you haven't tried another AC adapter, I would do that first. After replacing the AC adapter, check the DC jack for a high resistance using a good multimeter... A normal resistance would be around a half Meg ohm. If the internals are shorted, the resistance would be much lower. Unless you have the skill and tools to do surface mount soldering, I wouldn't attempt a repair

Thanks for a quick replay. I did try another ac-adapter with same result. With the male plug in and light went out on the ac adapter checking resistance between positive and negative it starts let say with half Meg ohm and it claims and claim higher and higher very fast. So like you sad it points to DC converters. I do have a skill to replace a surface chip I have done it before like a mosfats and diodes with some success. I know this is a hobby of mine and if you know which chip to replace I would really appreciate it. I would like to extend my knowledge and do more serious stuff like this. Thanks again

I haven't had too much luck finding Dell service manuals. If the DC jack is on a removable assembly, and not soldered directly to the motherboard, you will find a separate converter board piggybacked to the motherboard. This symptom you have is not common at all. The first thing to determin is if the conversion circuits are part of the motherboard or on a separate assembly...

Thanks for your help it helped me to look in a right direction and I think I got it.There are three same looking capacitors beside each other and one of them was faulty. Remove the one bad then solder a similar to it place and the AC adapter lite stays on and I can read voltage already on the motherboard. Now I will put it together and keep you updated if I did actually win this time. Oh one more thing you sad it is not very common I have seen already two Dell D600 with the same symptoms and this one.
Thanks again Tmagic650

That's great wrapmyride,
I haven't worked on many Dell laptops... It might be something common with Dell. Good luck

I don't know if it is common on Dells, but I have seen this problem twice before this one. It could had been something else twice before, but now I know what to look for next time. This one is together and working.

Thanks again Tmagic650

Ok wrapmyride,
glad I could help and I will keep this in mind if I run across one in the future...

hi guys,

great to see problems being solved. I wanted to add that this problem was a common problem with the d*00 series. I had alot of d600 and d400 with this problem on my desk.

mscrx, 19v short circuit problems are common problems for all laptops. they are connected with bad ceramic capacitors. but this case is lucky case of the problem solving. 19v bus located on all mb surface(this is due to that many PWM controllers eats 19v as their main input voltage), so when some capacitor is bad, the laptop completely dead. as for me, i solving such problems with "burning method".

donno if it is a common problem. I can only tell from my experience with dell laptops and I support 1500 of them (from c400 to m6300 including all d-series models) and only the d400 and d600 I found had this problem. the others work(ed) pretty fine and no problems liek that. just my experience...

.Thanks a lot for input on this problem guys, but can you Lamo be more specific on your "burning method". I know I got lucky to find that capacitor. In my case I did remove the black plastic from mobo where I was experting the problem and them I noticed one of the capacitor looked like had a left over glue from plastic on top of it. I did check the resistance on the bottom of the mobo and it was same resistance as other two, but on top of the capacitor was 0. Well soon I touch the top with tester the top kind fell apart. I think I got lucky there to locate it that way. That is why I would like to know Lamo method to locate them next time. Thanks again

wrapmyride, i can describe this method, but i warning you, that this method is dangerous if you don't know or don't sure where to connect + cable.
if you see, that resictance on the capacitor is 0 between + and gnd, do the following. you need good Power supply with voltage and current regulation. connect + of PS cable to positive field of capacitor(or to positive input of AC connector) and gnd to gnd field of MB. set the current of your PS to maximum, set the voltage regulator to minimum. turn on your power supply and start SLOWLY to increase the voltage of PS. don't forget to constantly check the current inceasing. when you reach current consumption near 1.5A stop to increase the voltage and begin to check capacitors(mosfets, resisotrs etc) for heating. i do it using my fingers
usually this method usable when you have some dead capacitors on 19v bus.

Attention! This method is VERY dangeous if you don't know WHAT EXACTLY you do! do it at your own risk.

Hi Lamo.
I am sure lot off guys will be happy to know this method. I know I am very happy and next time I will try it for sure. I do understand the risk involved, but you start with a dead mobo and you may end up with success or it will be still dead mobo. Again it is a hobby of mine and I like to learn new things all the time. This is a very good info for laptop repairs.
Thanks a lot again.

I have 6-7 Dell D800 motherboards with similar problems. Think you could fix them wrapmyride?

Hey wrapmyride, I found the faulty capacitor but how can you find the right replacement.

thanks

I believe Lamo would answer that question better. I would try to match it with a same looking one from a used mobo. I have few laying around just for that reason. But first if you can open a working D800 that would by the best to get the reading from that one to make sure what you looking for. Then check the one you want to use with the meter from used board so you know it is good and replace it. You can also try to find then in special electrical stores if you have any in your area, but I find it more harder find it there, because there is very few stores like that and they usually have small inventory.

My apology I was a way sorry for late reply. I would probably could, but Lamo would be better because he show me the way how to do it. I am still learning myself. It is still only a hobby for me. My record is from tree tries two wins one loss. But I have to admit those two wins felt good. You should try it your self I think its fun. I have to admit you have to understand the electronics little and keep learning and then practice soldering a lot.

Hi wrapwmyride

Have you heard about vga connector problem on dell d800. I have such problem . It is working ok if I push the vga cable upward when connected to my vga connector. I figure it is a loose solder probably. I have open the laptop down to the motherboard but found nothing obvious. I would like to fix it myself but am not sure where the connection pins are located on the motherbord itself in order to resolder them . Is there a way to find out . Do they publish schematic or something to follow somewhere
Thanks in Advance
from Ontario, Canada

usually ,you have 30-40 capacitors in MB at 19v bus. if one of them makes short circuit, you'll have to unsolder all of them. and this is useless. with the burning method you can find one faulty capacitor without unsoldering 30-40 small planar elements. and of course, you can find any faulty chips/mosfets/etc with this method. let's take some example: asus w3j. laptops wasn't react to power button pressing. there's short circuit in 3.3v bus. with this method, i found the dead ricoh r5c832 cardbus controller(a lot of heat). this took to me about 5 minutes.