T43 problem: no AC power

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pekelnik · #1 Post by **pekelnik** » Thu Apr 24, 2008 12:53 pm

Hello everybody.

I have a problem with my T43. It fell on the ground. Now it does not see AC power. The battery does not charge and it doesn't power up without battery.
Runs fine with battery though.
The problem is not a broken contact with the DC plug, as one would think.
I disassembled it, checked the internal wiring and it works. Also, putting it into a dock doesn't help either.

The OS doesn't mention any problem while running. The smapi chip seems to work, battery is reported, ac power is not.

Does anybody have any clue, what could be wrong? I suppose it's just a bad connection somewhere. Repairing seems to cost about 160$ just for the fact that somebody opens the chassis, even if he doesn't repair anything. I am afraid they would instantly change the motherboard and charge me at least 300$.
(In the worst case, I could by a motherboard online and just swap it)
Thanks..

jimmy274 · #2 Post by **jimmy274** » Thu Apr 24, 2008 1:39 pm

A fuse has gone out - either that or one of the PowerMOS transistors. I would bet on fuse - F2, F8 or F9 on the board - near the DC jack. Take a multimeter and check it out.

superboss · #3 Post by **superboss** » Fri Apr 25, 2008 1:44 am

Same thing happened to me but in my case, replacing the AC-adapter solved the problem.

pekelnik · #4 Post by **pekelnik** » Fri Apr 25, 2008 2:32 am

I tried 3 different AC adapters and a dock. I'm going to try the fuse now.
Just found out, that the batteries in my multimeter died. Grr.

pekelnik · #5 Post by **pekelnik** » Fri Apr 25, 2008 2:49 am

Does anybody know, where can I find the motherboard layout online? I don't have the original documentation with me (hopefully it's at home, but I'm not sure).

pekelnik · #6 Post by **pekelnik** » Fri Apr 25, 2008 3:31 am

Great! It's the fuse. Thanks.
What do I do with it now?

Probably need to get it fixed, right..

pekelnik · #7 Post by **pekelnik** » Fri Apr 25, 2008 3:44 am

If I could get a same fuse, I could solder it over this one (there's no way I could unsolder this one and put a new one over it). Or I could just bypass it. Any suggestions? I really don't feel like paying somebody 300CHF to change it..

#8 Post by **rkawakami** » Fri Apr 25, 2008 5:06 am

Well, I wouldn't bypass the fuse since it's there for a reason

. As I pointed out in this post at the Lenovo forum:

http://lnv.lithium.com/lnv/board/messag ... 5677#M5677

you can do all of the disassembly work yourself and then find a local radio / television / computer repair shop and ask them how much it would cost to solder on a replacement fuse. If you are lucky, you might even be able to find a university or trade school nearby that has an electronics lab and free (but skilled) students.

Getting the replacement fuse may be a problem. The cheapest method may be to buy a new fuse, if you can figure out exactly what it is AND find somebody willing to sell you just ONE. As you say, you could always buy another T43 motherboard and swap them around but that would be the most expensive fix. A middle ground would be to buy a "parts" or "repair" motherboard, pull off the fuse and hope that it is good. If the fuse that blew out on your board is like the F2 fuse in this thread:

http://forum.thinkpads.com/viewtopic.php?t=55504

then they are still available (at least here in the US). If the damage to the fuse was caused by mechanical stress from the fall, as opposed to an electrical short that occurred, then putting a new one on your board should fix your problem. If the short still exists, then your replacement fuse may have a very short life, or cause some other parts to blow up (read: MOSFETs).

Another "solution", although it may not be practical (or even possible), would be to try to use a docking station or port replicator and see if you can get power into the laptop that way. I'm not sure if the fuse that protects the DC power jack is also shared with the docking port connector.

pekelnik · #9 Post by **pekelnik** » Fri Apr 25, 2008 7:15 am

rkawakami wrote:Well, I wouldn't bypass the fuse since it's there for a reason . As I pointed out in this post at the Lenovo forum:

http://lnv.lithium.com/lnv/board/messag ... 5677#M5677

you can do all of the disassembly work yourself and then find a local radio / television / computer repair shop and ask them how much it would cost to solder on a replacement fuse. If you are lucky, you might even be able to find a university or trade school nearby that has an electronics lab and free (but skilled) students.

Getting the replacement fuse may be a problem. The cheapest method may be to buy a new fuse, if you can figure out exactly what it is AND find somebody willing to sell you just ONE. As you say, you could always buy another T43 motherboard and swap them around but that would be the most expensive fix. A middle ground would be to buy a "parts" or "repair" motherboard, pull off the fuse and hope that it is good. If the fuse that blew out on your board is like the F2 fuse in this thread:

http://forum.thinkpads.com/viewtopic.php?t=55504

then they are still available (at least here in the US). If the damage to the fuse was caused by mechanical stress from the fall, as opposed to an electrical short that occurred, then putting a new one on your board should fix your problem. If the short still exists, then your replacement fuse may have a very short life, or cause some other parts to blow up (read: MOSFETs).

Another "solution", although it may not be practical (or even possible), would be to try to use a docking station or port replicator and see if you can get power into the laptop that way. I'm not sure if the fuse that protects the DC power jack is also shared with the docking port connector.

Yes, that's a good idea. It seems to be exactly that F2 fuse, 1.1mmx1.6mmx3.2mm. I might buy a replacement and solder it on top of the first one. This seems to be a better idea to me, as I'm afraid I would burn or melt something on the board.

I tried bypassing it and it works. I'm sure it's due to the stress from the fall.
I still have those 3 MOSFETs around it intact

As I mentioned in the OP, I tried running it through a dock with no success.

Thanks a lot for the help. It saved me few hundred francs.

jimmy274 · #10 Post by **jimmy274** » Fri Apr 25, 2008 8:17 am

You're welcome, from me and Ray

I mainly use my hot air soldering iron for this kind of work, but it's still very touchy (I've bought the hot-air soldering iron just recently and I'm still learning).
Well, if you decide to travel through Serbia (:D), I would fix it for you, but since it looks like it's going to take a while before we enter the EU, and use it's benefits - chances are you're probably not going to travel through Belgrade anytime soon

Good luck with fixing that mobo!

pekelnik · #11 Post by **pekelnik** » Fri Apr 25, 2008 3:07 pm

jimmy274 wrote:You're welcome, from me and Ray
I mainly use my hot air soldering iron for this kind of work, but it's still very touchy (I've bought the hot-air soldering iron just recently and I'm still learning).
Well, if you decide to travel through Serbia (:D), I would fix it for you, but since it looks like it's going to take a while before we enter the EU, and use it's benefits - chances are you're probably not going to travel through Belgrade anytime soon
Good luck with fixing that mobo!

Thanks! I think I can manage it somehow. I'm not going to try to de-solder the old one though. I'll put the new one on top.
Anyway, Switzerland is not in the EU either.. It's really a bother. And while
Serbia will join at some point, Switzerland won't. (Some things are like 19th century here.. I'm Slovak, not Swiss)

T43 problem: no AC power

T43 problem: no AC power

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