Thinkpad T43 1871 does not see charger

[burns334]

Hello thinkpaders, I just picked up a nice used T43 that has a power problem and does not run off of the charger. When the charger is plugged into the unit absolutely nothing happens. It runs fine off of a charged battery. Does anyone know most likely cause? I have a spare T43 2668 motherboard I could replace it with if necessary.

TIA
burns

[RealBlackStuff]

Check the power fuses near the DC connector.

[burns334]

I know there pics of the fuses here somewhere and I will look for them but are the soldered to the MB?

Edit: I found it, now I need to look at the solder on the board

[poshgeordie]

The fuses doc is listed in the how to doc in my sig.

[burns334]

Morning guys, I've probed most of the fuses, especially the high power ones and do not see any problems, they all have continuity. Can anyone give me the fuse number of the most likely one to cause such problems? I'm almost ready to try a different DC power jack as its hard to tell if it picks up the ground properly from that side contact.

Thanks

[RealBlackStuff]

Use a multimeter and measure inside, on top of the white DC-powerconnector to the motherboard, if you get ~16VDC.
2 red wires are + and 2 black wires are -.

[burns334]

Thanks RBS, good news bad news, the DC jack is good, back to looking for a blown fuse.

[burns334]

Well it turns out that F2 is open and I tried to remove one from a donor board first as I thought it looked tough and I failed. So hard to get in there, I used solder wick and a microscope but I could not get it loose, any good tips from you pros?

burns

[burns334]

Update: Continued with efforts and decided that I could not remove the fuse without a good chance of damaging the board. I believe you need a device that would heat both pads at the same time and some very good skills. Anyway I decided to jump the fuse with a small piece of wire soldered to the top of the fuse and then put the laptop back together and all works normally now ie it charges and runs off battery alone. So now I have a T43 with an unfused area, how bad is that?

burns

[RealBlackStuff]

Very bad, and could cause a fire!
Get a replacement fuse (from mouser.com and the likes), and 'piggyback' solder that on top of the old one, instead of that piece of wire.

[burns334]

Very bad, and could cause a fire!
Get a replacement fuse (from mouser.com and the likes), and 'piggyback' solder that on top of the old one, instead of that piece of wire.

Great idea RBS, and now I know that's all that was wrong.

Thanks
burns

[burns334]

Well my replacement fuse came from mouser for a grand total of $0.65 and it was an exact replica of the one in the T43. I spent about 30 minutes relocating my stereo microscope, light and soldering iron to a very comfortable working height. I got all my equipment located just right and in focus for the job. I used about 25x and it took just a few seconds to get it soldered in place piggy back style. I then probed the pads on the board and I had continuity. I put everything back together and all works fine now, ye ha. I would not attempt this repair without a microscope and some good soldering skills but it all went well. Thanks for the good advice from RBS and poshgeordie.

Burns

[burns334]

Well after 5 weeks I have the no charge condition again and would guess that there is something else on the mb that blows the fuse. Think I will just go buy another mb and get rid of this problem unless someone has some good ideas.

burns

[poshgeordie]

Something is drawing excess current, and I'd suspect the battery itself.

Why not solder another fuse in place and use Battery Maximiser to see what current the battery is drawing when charging and report back.

Have you, or are you currently using the battery as in your Battery Problem post?

If not, Is the battery a genuine IBM one or a cheap Chinese (rubbish) one?
A lot of eBay based Chinese ones are nasty, and proves that cheap ends up being expensive in the long run.

[burns334]

Something is drawing excess current, and I'd suspect the battery itself.

Why not solder another fuse in place and use Battery Maximiser to see what current the battery is drawing when charging and report back.

Have you, or are you currently using the battery as in your Battery Problem post?

If not, Is the battery a genuine IBM one or a cheap Chinese (rubbish) one?
A lot of eBay based Chinese ones are nasty, and proves that cheap ends up being expensive in the long run.

Hi Nick, the problem battery got tossed out immediately, this is a old genuine Lenovo, I'll solder a new fuse, I bought 2 and try the battery maximizer. What current should I see as a normal charge?

TIA burns

[poshgeordie]

I knew you'd ask the current - short answer is I don't know!! Around 1.5A but what would be useful is if you could report your readings back and it may jog my (and others) memory.

Do you have more than one battery and do a comparison of the readings? If so try and discharge the batteris so they are at similar percent charge - eg both 70%.

Other than examining the battery and being able to eliminate it, it's hard to then say what the issue could be.

One other thing does occur to me though. at the rear of the planar where the DC Connector wires pass over the planar there's supposed to be some tape over three SMD capacitors. It's possible that if that tape's missing, there could be a danger of short circuiting between the DC connector pins and the caps.

[burns334]

Nick, the readme for battery maximizer looks like it does not support the T43 unless it is running NT or any of the 1871 models.

burns

[poshgeordie]

Surely it's there as part of the XP package for all T4x models?

[burns334]

Surely it's there as part of the XP package for all T4x models?

My bad, I found it, thanks

I could just put that battery in another Thinkpad and see what it draws, no?

[poshgeordie]

You could do but it may take the fuse out on that one too!

[burns334]

You could do but it may take the fuse out on that one too!

Nick, well that's what I was thinking but I do have a T43 I was planning on putting in a motherboard because it occasionally freezes up, ie. I won't lose much

burns

[burns334]

Nick, I think things went normal, I plugged in the charger when the battery was at 80% and it started charging at 2.5A and 12.27V and within a minute it had cut back to 2.0A. After about 3 minutes it cut back some more to 1.65A and 12.4V

burns

[poshgeordie]

Those figures sound normal to me.

Assuming there's not a current spike at some point which causese the fuse to blow, it's v difficult to know what to suggest now.

Maybe the only thing is to use the machine without the battery for a while and then see what happens; this will tell you if you have a hardware or battery issue.

[burns334]

Nick, can't run on charger, machine will only run off a battery, see the problem?

burns

[poshgeordie]

Ah then could be anything!