T43 model 2668 fails to charge battery

[SJRoome]

Hi

I recently bought a used T43 model 2668 on eBay and it turns out to have a battery charging problem. The laptop will run from the battery or from mains power, but will not charge the battery. I have another T43 so I can substitute the battery or charger and I currently charge the battery using the other laptop.

The battery status light appears to reflect the charge state of the battery although it is always illuminated if there is a battery present whereas my correctly functioning T43 does not show a status light when the laptop is powered down and the charger is disconnected.

The battery status shows a battery voltage of 11.6V, status "charging", but no charge current. This is not affected by changing the battery or the charger.

I have opened the laptop and pin 24 (switched mode output) of the ADP3806 battery charger chip is also 11.6V, and there does not appear to be any voltage on pin1 (VCC). A small area of the PCB to the left of the ADP appears heat damaged when viewed under magnification, but the relevant track tests OK. The area feels hot to a finger, but looking at the motherboard pictures here http://nickpaton.fireflyinternet.co.uk/ ... 0Fuses.pdf. there does not appear to be a component located on the other side.

The following is a clickable thumbnail showing the area that appears heat damaged.



Any ideas what could be wrong? I will risk further disassembly if there is likely to be an obvious cause that I could correct, but replacing the ADP3806 is beyond me and a replacement motherboard will not be cost effective. The only other problem with the motherboard is that the broadcom gigabit ethernet is not detected.

Steve

[scr71822]

I have an R51 that I am having the same issue with but no heat damaged areas. On Monday I am going to replace the FDS6990A located on the back of the motherboard. I replaced the ADP3806 with no effect at this point.

http://forums.thinkpads.com/viewtopic.php?f=2&t=70832

Check out this thread.

[poshgeordie]

Hi Steve and welcome to the forums.

Could you possibly modify the photo to fit in with forums rules:

5. IF you must add a photograph to your post, PLEASE limit the size to 50k or less and place a warning in the subject line.

Also PM sent.

[scr71822]

I replaced the FDS6990A located on the back of the motherboard, and it doesn't seem to have fixed the problem, however the ultrabay battery looks like it is fine now, I'm going to do some more checking to see what else may need to be replaced.

[SMA]

Steve

When an area of the board is getting warm then that can only mean that some energy is being wasted.
That is, when running the T43 from the battery, then the battery will drain faster than it is supposed to.

It is easily seen from Nick's fuse diagram that some boards do not have a component on the bottom side of the board below
the area that is getting warm, but other boards do have a component there.
My immediate guess is that boards with GigaBit LAN do have a component there.

The component on the bottom side of your board should be of a type similar to this damaged inductor

link to picture of damaged inductor

There should be two of these inductors.
The one that is possibly causing you troubles is only partially visible in the picture,
but it is sitting in the upper left part of the picture - below the finger.

If you do have a shorted inductor, then I will expected that it can just be removed and you can do without it, since your LAN
interface is already malfunctioning.

If there is no voltage on pin 1 of the ADP3806 when the AC Adapter is connected, then that is another problem that
must be fixed before the battery charging process can start. I believe that that might be fixable, but I also believe that
the heat problem should be solved first.

[SJRoome]

Hi

Thanks for your replies. I just carried out my first motherboard removal. Here is a clickable link to the reverse of the board.



There is no obvious damage and when I connected a power supply and powered on there was nothing obviously hot.

I cleaned the top of the motherboard with IPA and examined the area that looked damaged under a microscope. Two of the through-hole plated holes have obviously had very heavy current, on one enough to evaporate a third of the surrounding pad, so unless anyone has any clever ideas I think I will have to run this one without a battery. There is one thing I could do with immediate help with. When I pulled the motherboard out a soft black rubber item came out, apparently from under the motherboard. Anyone able to tell me what it is and where to put it as I cant work it out?





Thanks Steve

[RealBlackStuff]

That goes on the top left of the mobo, around the microphone.

[SJRoome]

Hi

Thanks.

Steve

[poshgeordie]

Do the burnt plated through holes go right through the board?

If so run a single strand of v thin wire through the hole and solder each end to the corresponding solder pad.