Another random shutdown [T40]

[okkyn]

Hi all,

My old trusty T40 finally experience random shutdown

OK, my diagnoses and troubleshot are:

- It is not OS/software related. I have XP and ubuntu on my 2nd HDD and they behave the same (ubuntu always shut it down during boot).

- Not an ATI graphic chip's cold solder problem. I pressed the keyboard above the chip, nothing happened. It sometimes shutdown even when I didn't touch the laptop.

- It is not related to CPU heat or fan as the shutdown often happened during startup/boot, and the CPU temp reading was low. I even reapplied AS 5 paste to the CPU.

- Replaced RAM, no effect.

- Removed WIFI card, emptied ultrabay, swapped HDD, no effect.

- Swapped the CPU (I upgraded to Dothan 1.8 and still keep the Banias 1.3), worse, the old CPU always shutdown during boot.

Now, it appears the last symptom says something. I set my laptop to always run at low CPU speed (600 MHz) using thinkpad power managament, and voila... the shutdown was disappear!
Well, sometimes the shutdown comes again when I run CPU intensive program or watching video, but lot less happen.

Any of you experience the same thing? I searched the forum, and from what I read, it possible that the MOSFET voltage regulator, specifically the one that regulated CPU voltage is almost gone (half working). If time permit, I will replace these MOSFETs and post the result. Meanwhile, I must be happy with (very) slow thinkpad...

Additional info, when it shutdown, I must disconnect power supply adapter and sometimes press the power button long enough.

Thanks,
Okky

[sktn77a]

Sounds like overheating or graphics chip problem. Just because nothing happens when you press the chip, and it sometimes shuts down when you don't, doesn't exclude this. Do you have a temperature monitoring program?

[okkyn]

Sounds like overheating or graphics chip problem. Just because nothing happens when you press the chip, and it sometimes shuts down when you don't, doesn't exclude this. Do you have a temperature monitoring program?

Thanks. Yes I do, I use T43 fan controller. I didn't record the temps, but it seems normal.

[okkyn]

Yesterday, I took a plunge and buy a Black & Decker heat gun. After dismantling my T40 and removing the motherboard, I blasted it with hot air. Started blowing hot air at distance to warm-up motherboard, and then continue to focus the hot air around GPU. It took approx 5 minutes.

After cool down, connected LCD, keyboard, memory, CPU, hardisk and backup battery... and... it booting!! Tried to run under full speed CPU, still worked (before it immediately shutdwon). I played around with it the whole evening, it never shutdown again. Hopefully it will stay working... my finger crossed

Now I have 2 thinkpads... I bought used T42 to replace my broken T40. I think I will give the T40 to my wife...