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PostPosted: Tue Mar 25, 2008 1:50 am 
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A piece of foil that hit my VGA RAM shorted out something on my T41 because now it won't even power up does the T41 have any kind of fuse protection for surges?
what should I look for I have it apart right now hoping the MB isn't toast :( thanks


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PostPosted: Tue Mar 25, 2008 2:04 am 
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Haven't spent too much time looking closely at T4x motherboards but this is what some of the fuses in a T23 look like:

http://www.rkawakami.net/ibm_t2x/main_fuses.jpg (highlighted in blue boxes)
http://www.rkawakami.net/ibm_t2x/let.jpg (at the middle-top of the picture, to the left of the label F2)

Fuses generally are labeled with "F" numbers. Finding them is a matter of scanning around the motherboard. Figuring out what they are (the current rating) can be easy in the case of the white ceramic fuse with the silver endcaps (it has 10A on it; 10 amps) or next to impossible (like the F2 fuse which has an "FU" code on it). Also, it's been my experience that the fuse is one of the last things to blow out when there's a short or power problem.

To answer your other questions in the other post I just locked... I don't know of any photos/scans which detail the exact locations of all of the fuses on a T41 motherboard. Maybe somebody will post that information. Replacing them requires a fine-tipped soldering iron, a steady hand, tweezers or needle-nosed pliers, good eyes and a bit of luck. Surface mount components are not as easy to work on like "through hole" parts since most of the area which is attached to the motherboard is resting on the surface of the board. That makes getting them off and on the motherboard a bit harder.

Once you locate them, you can test them with an ohmmeter. Zero ohms (or very near zero) indicates that the fuse is still intact; anything other than that is an "open" and means the fuse is gone. Recently Merlin Witt posted a warning about checking some of the very low current fuses using a multimeter. Apparently it is possible to blow the fuse simply by trying to check them:

ref: http://forum.thinkpads.com/viewtopic.ph ... 438#402438

I haven't run into that problem yet, but then again I don't know how much current my meter is providing when it is in the lowest resistance range.

Also, here's a recent thread about T42 fuses:

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

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PostPosted: Tue Mar 25, 2008 4:25 pm 
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Ok, Ray, I just wanted to inform you that I found a problem with the T41 I own - it was a fuse! Actually, I changed the P channel MOS transistor (TPC8111) too, but I doubt that it's fried. The best way for anyone to change a fuse is to buy a dead motherboard and simply replace the dead fuse with the good one by using hot air. The fuse that got burned is the one labeled F9 (just underneath the battery jack).

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PostPosted: Tue Mar 25, 2008 5:03 pm 
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That sounds great! Of course the danger in buying a "dead" motherboard is that it could have the same issue that you are having and you would be getting another broken part (fuse, MOSFET, etc.). The main problem with replacing a known bad fuse is that you don't know if the reason that the fuse blew is still present (i.e., a short still exists somewhere).

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[DONOR] X22;X24;X31;X41;X41T;X60;X60s;X61;X61s;X200s;X300;X301;Z60m;Z61t;Z61p;560Z;600;600E;600X;T21;T22;T23;T41,T410;R50;A21p;A22p;A31;A31p
NOTE: All links to PC-Doctor software hosted by me are dead. Files removed 8/28/12 by manufacturer's demand.


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PostPosted: Tue Mar 25, 2008 6:22 pm 
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Actually, there's a lot of fuses and MOSFETs on a motheboard that are of the same type - if you have a problem with one or two components, it's very likely you'll find them alive on a dead board. Secondly, even IBM had problems with different components - I found out that a lot of parts (fuses, MOSFETS) are varying depending on the year the laptop was made - for instance, the same fuses are on both T40 and R51, while the T41 has different fuses. I think that somwhere in 2005, IBM stopped installing TPC MOSFETs (Toshiba), and started with Fairchild, but still there are boards with both of the types...
Another good thing you've mentioned is that the problem is usually unknown - we don't know why did the fuse blow, but luckily for me - I do know... I did some things with a serial2serial (USB on laptop) cable and connected the laptop to my desktop. Unfortunately, the laptop was on battery power, which further means that it's Ground is "floating" - most of the people reffer to it as Virtual Ground, while the desktop had his ground in the power outlet. This is the worst thing you can do with a serial cable - the current that passes through the Ground could be very, very high, and of course - burn something. And that's exactly what happened...

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[Ex] ThinkPad T41 2373-TG5
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"People can have the Model T in any colour - so long as it's black."
Henry Ford


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 Post subject: what happened in detail
PostPosted: Tue Mar 25, 2008 11:31 pm 
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Ok here's what I was doing when it went dead in detail
feel free to burst into laughter since it was pretty stupid on my part.

First off I had my 41 plugged in with the keyboard aside so I could push down on the vga RAM which now only worked only if I pressed hard
so for whatever reason I took a square piece of foil the size of the ram
and used a small bic lighter to slowly heat the chip
of course I left the laptop on like a genius the foil hit something and poof no power up I'm just assuming I toasted the mb
but if I was to look somewhere first fuse etc where should I start
since it's all apart right now?


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PostPosted: Tue Mar 25, 2008 11:46 pm 
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djtopcat wrote:
Ok here's what I was doing when it went dead in detail
feel free to burst into laughter since it was pretty stupid on my part.I'm just assuming I toasted the mb
but if I was to look somewhere first fuse etc where should I start
since it's all apart right now?


Don't feel too bad...the other day I spent a half hour looking for my glasses, and then realized I WAS WEARING THEM!


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