Question Thinkpad T40 turns off after a few seconds and will not turn on till power cord is unplugged/replugged ?

Mar 29, 2023
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Hello guys. I've got issue with my old Thinkpad T40 laptop with no battery. It turns off after 1-2 secs after I press power button. At start some actions occur - led lights, fan rattles, display stays blank and suddenly it's game over. After that, I can't start it again with power button unless I unplug power cord and then plug it in again. I replaced the PSU but no luck.
However, when I start the laptop with no ram, it beeps and stays powered on. What da hell is goin on?
 

Cj-tech

Admirable
Jan 27, 2021
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8,940
Hello guys. I've got issue with my old thinkpad t40. Laptop with no battery turned off after 1-2 secs after I press power putton. At start some actions occur - led lights, fan rattles, display stays blank and suddenly game over. after that, i can't start it again with power button unless I unplug power cord and then plug again. I replaced a PSU, but no luck. However when start my laptop with no ram, it beeps and stays powered. What da hell is goin on?
Did you upgrade any of the hardware recently? Laptops are much more difficult to diagnose because of the compactness and lack of compatible parts. Does it boot entirely when it does turn on or does it stop before you can login? If it’s the latter, it sounds like the HDD/SSD could be bad or you need to reinstall the operating system.
 
Mar 29, 2023
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No upgrades were done. While testing I removed all the hardware parts - ram, hdd, dvd, wifi. I tried another cpu, held power button for 30 secs. Every try displays nothing on the screen. Google said it might be electric short or capacitors overcharge but it's beyond my skills.
 

Cj-tech

Admirable
Jan 27, 2021
534
67
8,940
No upgrades were made. While testing I removed all the hardware parts - ram, hdd, dvd, wifi. I tried another cpu, held power button for 30 secs. Every try displays nothing on the screen. Google said it might be electric short or capacitors overcharge but it's beyond my skills.
You can try a bios reset by removing the CMOS battery for 30 seconds. However, I’ve had bad motherboards with the same symptoms, so I would not get your hopes up. Another point of failure could be the connection between the power cable and the port on the motherboard. I’d double-check that it’s not damaged or loose.

View: https://youtu.be/76I2Ec9K7lw
 
Mar 29, 2023
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You can try a bios reset by removing the CMOS battery for 30 seconds. However, I’ve had bad motherboards with the same symptoms, so I would not get your hopes up. Another point of failure could be the connection between the power cable and the port on the motherboard. I’d double-check that it’s not damaged or loose.

View: https://youtu.be/76I2Ec9K7lw

Yes, i tried with no CMOS battery.
I replugged power connector. Either way, no changes.
Ultimately I can't realize why laptop being started with no ram stays powered after it makes several beeps - fan rattles led lights - if there is a power problem.
If there is not a power problem - why i can't start it until I unplug/replug power cord ?
It looks like a fault happens during POST next step after the memory check. may be BIOS is corrupted?
 

Cj-tech

Admirable
Jan 27, 2021
534
67
8,940
Yes, i tried with no CMOS battery.
I replugged power connector. Either way, no changes.
Ultimately I can't realize why laptop being started with no ram stays powered after it makes several beeps - fan rattles led lights - if there is a power problem.
If there is no a power problem - why i can't start it until I unplug power cord.
It looks like a fault happens during POST next step after the memory check. may be BIOS is corrupted?
Can you boot into the bios with RAM installed? If you have a USB drive, you could try installing a Linux distribution such as Ubuntu on it. Ubuntu allows you to run the operating system directly off the USB stick without installing it on the SSD/HDD.
 
Mar 29, 2023
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I've discovered a new situation - laptop only starts with external monitor but internal lcd remains black. OS loads.
If I switch in BIOS to internal LCD laptop shuts off after 1 sec since power on.
 

Cj-tech

Admirable
Jan 27, 2021
534
67
8,940
I've discovered a new situation - laptop only starts with external monitor but internal lcd remains black. OS loads.
If I switch in BIOS to internal LCD laptop shuts off after 1 sec since power on.
It definitely sounds like a power issue… It’s possible that the LCD is pulling too much power and the motherboard has a short in it. Personally, I’d have given up before now and called the laptop dead. However, if you can boot into Windows using the external monitor, try using the Lenovo update tool to update your BIOS and drivers.
 
Mar 29, 2023
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It definitely sounds like a power issue… It’s possible that the LCD is pulling too much power and the motherboard has a short in it. Personally, I’d have given up before now and called the laptop dead. However, if you can boot into Windows using the external monitor, try using the Lenovo update tool to update your BIOS and drivers.
Thank you very much for assistance.
I've checked your guess. I unplugged display cable from motherboard to exclude any chance of a power drain or electric short of display system or inverter board.
But laptop still shuts off after 1 sec since power on. And starts with external monitor.
Looks like onboard ATI gpu is somehow faulty