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ThinkPad T43p turns on for 1/2 second then goes off

T4x series specific matters only
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kfzhu1229
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ThinkPad T43p turns on for 1/2 second then goes off

#1 Post by kfzhu1229 » Sat Apr 25, 2020 12:08 am

So the story is as follows: I have had a T43p as my daily driver until that motherboard developed GPU soldering issues (this isn't corrupted picture or something like that, but rather video would go off completely to a black screen when the chassis is flexed, and then it may or may not come back). I have since retired that as a daily driver and replaced its motherboard while I was in China.
Now seeing I barely have much to lose with this motherboard, I attempted the oven method. After letting it completely cool down, the board worked perfectly with no black screens. However, after I assemble the motherboard into a base cover, the motherboard wouldn't work anymore. Now it just comes on for 1/2 second and then shuts off, the same behaviour as if the CPU is not installed.
I have tried the CPU in a Latitude D610, works perfectly fine. I have sprayed the socket with contact cleaner, no difference. I have removed everything (including the RAM) except the CPU and the heatsink, no difference. I have checked many voltages off the schematics and they all look like they are present (however I noticed the CPU voltage can't exactly reach any expected values in that 1/2 second before the thing shuts down). I have bypassed the AC/battery power MOSFETs, still shuts off.
Is there anything else I can try for this board? I already have the replacement, but seeing it is a T43p board it would be nice to get that working.
Dell Lat CP MMX-233 64mb 40gb W2k
600 PII-266 416mb 40gb WXP
T23 PIII 1.13ghz 1gb W7
Lat D830 X9000 8gb 128gb WSXGA+ Ultrasharp fp W10
T530i 15.6" i7 16gb fp W10
UXGA:
A30p PIII 1.2 1gb W7 (IDTech)
T43p 2.26 2gb fp W10 (Sharp)
Lat C840 P4-2.5 2gb 60gb W7 (Ultrasharp)

RealBlackStuff
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Re: ThinkPad T43p turns on for 1/2 second then goes off

#2 Post by RealBlackStuff » Sat Apr 25, 2020 1:59 am

Southbridge (big Intel chip under the wifi-card) could probably do with extra pressure or a "rebake".
Lovely day for a Guinness! (the Real Black Stuff). And pigs CAN fly!
Check out The Boardroom for Parts, Mods and Other Services.

"Computers don't lie, but liars can compute." (Terry Hayes: I Am Pilgrim)

kfzhu1229
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Location: Toronto, Canada

Re: ThinkPad T43p turns on for 1/2 second then goes off

#3 Post by kfzhu1229 » Fri May 01, 2020 2:01 am

RealBlackStuff wrote:
Sat Apr 25, 2020 1:59 am
Southbridge (big Intel chip under the wifi-card) could probably do with extra pressure or a "rebake".
I thought so too.
Yesterday I was doing baking for a T42 motherboard with the exact same symptom of the screen blanking out when the board is flexed and that one worked as soon as it is cooled down! Put a little heatsink on the 7500 chip and hope for the best.
I thought I will do a rebake with the T43p motherboard after that success, but unfortunately absoloutely nothing changed.
Then since I barely have much to do in this pandemic anyway, I was reading the schematics of this board and seeing what was causing the shutdown. Here in this screenshot there is this pin called PWRSHUTDOWN which might give me a clue about this shutdown issue, so I used my multimeter and observe. When AC or battery is inserted, I see 3.3V on the pin. When I press the power button, the pin is 0V as soon as the board shuts down and never comes back until I replug the power (and also the power button is not responsive until I replug the power). Switching it to resistance mode I see infinite reading when there is no power, and 10 Ohms when the board shuts down after the press of the power button.
Since I have nothing to lose, I tried connecting that pin to a CR2032 coin cell and the screen came on when I press the power button this time!
However, now the board shuts down exactly when it finishes POST (it shuts down when displaying the message of date and time error and exactly when you can press F1 to go to setup, no matter how long or short the POST takes). But on the flip side it seems like the oven worked for the graphics chip that now I try to bend the board back and fourth and no screen blanking anymore!
So this seems like something is shorting out that pin to get the SuperIO and MOSFETs to shut down the board. What can be wrong here? The graphics and southbridge seem to work just fine as bending the board does nothing.
By the schematics, there are exactly 5 places where this pin goes to: Two transistors: one by the power MOSFETs, one by the miniPCI slot; SuperIO (IBM PMH_6), Toshiba power management chip (TSURUMAI), MAX1901 power supply
https://1drv.ms/u/s!At7-rt1KJ7WviPhGXqg ... Q?e=SuYXu9
Dell Lat CP MMX-233 64mb 40gb W2k
600 PII-266 416mb 40gb WXP
T23 PIII 1.13ghz 1gb W7
Lat D830 X9000 8gb 128gb WSXGA+ Ultrasharp fp W10
T530i 15.6" i7 16gb fp W10
UXGA:
A30p PIII 1.2 1gb W7 (IDTech)
T43p 2.26 2gb fp W10 (Sharp)
Lat C840 P4-2.5 2gb 60gb W7 (Ultrasharp)

RealBlackStuff
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Re: ThinkPad T43p turns on for 1/2 second then goes off

#4 Post by RealBlackStuff » Fri May 01, 2020 2:20 am

Bad wifi-cards have been known to cause similar mayhem.
Lovely day for a Guinness! (the Real Black Stuff). And pigs CAN fly!
Check out The Boardroom for Parts, Mods and Other Services.

"Computers don't lie, but liars can compute." (Terry Hayes: I Am Pilgrim)

kfzhu1229
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Location: Toronto, Canada

Re: ThinkPad T43p turns on for 1/2 second then goes off

#5 Post by kfzhu1229 » Sat May 16, 2020 10:05 pm

RealBlackStuff wrote:
Fri May 01, 2020 2:20 am
Bad wifi-cards have been known to cause similar mayhem.
Hmm well I gave up that day and didn't continue until now.
You said that a bad wifi card can cause this problem, and that according to the schematics, there is one transistor that is connected to pwrshutdown (which is the trace that I am finding out why its 3.3V voltage got brought down and semi-shorted to ground when I press the power button) called Q59, so I started by disconnecting that transistor. And now the board starts up without the need of an external 3.3V power supply to maintain 3.3V on that pin, but it still shuts down at the very same stage.
Now I see that that transistor is connected to a temperature sensor chip MAX1989 (To "ALERT" pin). Am I looking at some thermal sensing problems here or something? And when something overheats, can the board shut down during POST or must it shut down after POST like when it is shutting down now?
Just so it is clear in the image below is the transistor that I took out where it is surrounded by flux, and also here is the corresponding section of the schematics:
https://1drv.ms/u/s!At7-rt1KJ7WviPhsWVT ... Q?e=u22LP7
https://1drv.ms/u/s!At7-rt1KJ7WviPhrXUp ... g?e=smhWgj
Dell Lat CP MMX-233 64mb 40gb W2k
600 PII-266 416mb 40gb WXP
T23 PIII 1.13ghz 1gb W7
Lat D830 X9000 8gb 128gb WSXGA+ Ultrasharp fp W10
T530i 15.6" i7 16gb fp W10
UXGA:
A30p PIII 1.2 1gb W7 (IDTech)
T43p 2.26 2gb fp W10 (Sharp)
Lat C840 P4-2.5 2gb 60gb W7 (Ultrasharp)

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