After the T400 restarts normally, only the power light and Bluetooth light battery light are on, but

1. First of all, it is recommended that you release static electricity to the fuselage before turning on the machine, the method is: disconnect the power adapter and other wiring, unplug the battery, press the power button 10 times, press once every two seconds, and then only connect the power adapter, press the power button to turn on, and detect whether it can be turned on normally. Then turn it off, after only installing the battery without connecting the power adapter (to ensure that the power in the battery can ensure normal power-on), press the power button to power on and check whether it can be turned on normally.

2. Please press F8 to enter the Windows Advanced Boot Menu when the Lenovo logo appears when you boot the phone, select "Last Correct Configuration" and press Enter to enter the system.

3. Please uninstall the recently installed software and test it to see if the fault disappears.

4. Enter the startup items to close the files that are not often used recently, the method is: "start" point "run" enter msconfig and then hit enter, in the open startup items, cancel the checkmark before the recently used files, it is recommended that you keep the input method and the startup items of the antivirus software, the others can be disabled, and then restart after shutting down for testing.

5. It is recommended that you enter the safe mode regularly to check and kill viruses, and the method is: press F8 to enter the safe mode when the Lenovo logo appears at the boot.

6. If none of the above methods can be booted normally, it is recommended that you back up the personal important data of the C disk and the desktop, use the pure version of the system CD, use the optical drive to boot and reinstall the system for testing, and install the steps of the operating system

XP system installation.

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It may be that the motherboard is over-powered and needs to discharge the BIOS, but it can't be completely**. At the moment I don't know of a good way to be completely**.

Notebook research and development, professional answer:

There are many possibilities when booting up.

1.The hard disk is spinning, the fan is spinning, it means that the power-on timing process has passed, and it is time to boot self-test, whether there has been a boot self-test, it is not clear (you need to disassemble the motherboard and use the debug card to see which step to run).

2.If you hear the sound of entering the system any longer, it means that the motherboard is OK, and it may be a problem with the screen and cables.

3.If it has been hanging like this and there is no response, it means that it is a problem with the signal on the motherboard, clock signal, reset signal, etc., and you need to use an oscilloscope, because these signals are not there, the chip will not work, and it will show that a few lights are on.

4.If it will automatically restart after a while, it is a problem with the hardware itself, because some important hardware that cannot be ignored during the self-test process cannot be checked (CPU, chipset, graphics card) will be restarted and rechecked, and the specific one also needs to be inserted into the debug card to see.

5.The only thing you can do for the time being is to hope that a chip is protected and there is no display on the boot, so that you can unplug all the battery power, and then press and hold the power button for 5 seconds + discharge, and then plug in the battery separately and plug in the power supply separately to power on and try it.

If 5 doesn't work, that's the possibility of 1, 2, 3, 4, all need after-sales maintenance.

There are many reasons why the computer can't be turned on and the screen doesn't respond, one, the system is damaged, the hard disk is damaged, the notebook can't recognize the hard disk, etc., second, the memory is broken or the memory slot is soldered, and then there is a problem with the motherboard power supply chip, and third, the BGA (north-south bridge, graphics card, network card, etc.) packaging chip virtual soldering damage will cause the boot screen to not light up. It is recommended that you send it for repair and testing.

I'll help you in Beijing.

If you are not in Beijing, it is recommended that you find a reputable and skilled repairer to help you overhaul.

First, switch the screen, press the fn+switch screen key (different computers, it is between f1-f12).

If it doesn't work, then test whether the screen is broken.

Take a desktop monitor and plug it in, press the fn+ switch screen key (different computers, it's between f1-f12), and see if the new monitor can display normally, if not, then you have to take it to the repair place to see if the graphics card is broken or the monitor is broken or something else.

I guess your computer is going to take a lot of time. This fault has nothing to do with the scheduled shutdown you set earlier.

Solution: 1. Unplug the power plug and unplug the battery.

2. Use a screwdriver to open the memory cover behind the computer and remove the memory.

3. Use the eraser to erase the gold finger part of the memory, plug it back into the memory after wiping, and connect the power supply. Boot troubleshooting.

If there is a problem with the high-voltage board or motherboard, you will be provided with free detection of the specific fault.

I haven't seen a problem with the display. There's nothing, and there's no way to fix it, so it's better to send a warranty.

Belch... If you don't have tools, you can't disassemble it, so it's recommended to send it to a repair shop.

This is caused by a hardware failure of the computer, and it is recommended to use the following methods to detect it:

1. Look carefully at the screen to see if there is a very dark desktop image.

If there is, the screen light is broken, and it will be done by finding a repair and replacement of about 100.

2. Remove the battery and restart it with the power supply. If it can't be turned on, it is recommended not to disassemble the machine yourself and take it to a professional maintenance personnel to solve it.

Plug in the memory first, and then connect the external monitor, if the monitor has a display, say that there is no problem with the obvious card and motherboard!

Now the screen and screen cable are left, and there is already a system problem.

Here first, the optical drive boots the operating system to troubleshoot system problems.

If you change the system and it still doesn't work, the display and cable are left.

If you have strong hands-on ability, you can disassemble it yourself and unplug the screen cable connector. See if it's normal.

It's not normal.,Just buy a screen about 500 to get it.。。

Of course, it won't be sent for repair.

Hope it helps!

My legion, helping others!

I also have a machine with the same problem as you.,I suspected that there was a problem with the graphics card.,Later, I did it slowly.,Find an acquaintance to get it.,Confirm that one of the memory is broken, I added a memory myself.,The bottom heat sink is always blown in the memory position.,Serious dust accumulation leads to a broken one.。

Just swap this memory out.

You have to go back to the after-sales service to deal with this problem, and I personally think it is still a problem with the cable!

Where is the problem of short circuit in your computer, so BIOS battery protection, you go to the local computer city to have a look, it is not good to always get your computer like that!

Oh my God, what kind of machine is this, let's go to the pit and see. Maybe get a free one or something. It is estimated that there is a problem with the graphics card.

The fault point can only be determined after the specific test is required.

There is a greater chance that the graphics card will be desoldered.

The graphics card or CPU fan is damaged, and the temperature is too high to turn on.

There are many reasons for the black screen, it may be a hardware problem, or a setting problem, caused by too much dust It is recommended to clean up the dust first, boot up and press F8 to enter the safe mode to use the machine to see if there will be a crash, if there is a format of the hard disk installation system after saving important files to see if it can be solved, if not, you can try to do a full check to kill the virus and close the unwanted boot startup items to see.

There is a problem with the memory module or graphics card. Check first to see if the memory module is not plugged in properly, try to change the slot, if not, change the memory.

Preliminary consideration of a few possibilities:

1. Display problems, screen, wiring, graphics card;

2. BIOS problem, if the BIOS fails, it may also lead to a black screen;

3. The failure of the hard disk, if the hard disk has a problem, the data cannot be read, how to solve it? Try an external monitor, if you can use it, you enter the BIOS, if you can enter, there is no problem with the BIOS, one of the BIOS is the hard disk detection, detect whether there is a problem with the hard disk, this detection is still more practical. If there is no problem with the hard disk after testing, it is a problem with the display or cable, and the probability of the graphics card failure is not high.

Maybe there was a problem with the hard drive, my classmate did this last time, and then changed to a hard drive.

This situation is generally a graphics card issue and can be fixed.

It must be a hardware problem, fix it. It can't be solved here.

Remove the battery, put it for a while, connect the adapter power supply directly without the battery, and try again when you turn it on.

Boot up and press F8 to select safe mode, can I enter the operating system? If you can recommend that you do a full antivirus in safe mode and turn off unnecessary boot items to see if this problem can be solved, if the above operations cannot solve this problem, it is best to save the important data and reinstall the operating system; If you can't even enter the safe mode, then you have to find a way to save the important files and reinstall the operating system.

1. Use a multimeter to check whether the socket is normal and whether the power supply voltage is 220V

If the mains voltage is abnormal, it is recommended to replace the use environment test.

2. Use a multimeter to check whether the output voltage and current of the power adapter are consistent with the labeled.

If the gap is very large and the mains voltage is normal, it can be judged that the power adapter is faulty and the laptop power adapter needs to be replaced.

3. If the above checks are normal, remove the laptop battery and do not connect an external adapter.

Press and hold the power on/off button for 5 seconds and repeat 3 times. After releasing the residual charge of the notebook, plug in the power adapter separately and power on for testing.

4. If the fault persists, check the power interface of the notebook to see if it is abnormal.

For example, looseness or cosmetic damage.

5. The above checks are normal, and basically it can be preliminarily judged that the notebook motherboard is faulty. It is recommended to send the service station for repair.

Check if an external monitor is available?

The fault is very obvious, and the motherboard graphics card is broken.

If the system junk files occupy too much CPU, clean up the system junk or install a new system from scratch.

Dear users, hello!

In this case, you can back up your important data to a USB flash drive or other device first, and then check whether it is normal after resetting the operation

Reset operation method: first turn off the machine, and then reset.

Unplug the power supply, batteries, and other external devices from the computer (make sure the power is completely off); Then press and hold the power button for about 20 seconds; After that, connect the power supply and battery to the machine, and then turn it on.

If this is still the case after the reset, there is a high possibility of hardware problems, it is recommended that you go to the service station in time to let the engineer help you detect and deal with it.

Service station address inquiry.

It is estimated that the battery has run out of power, and the alternating current has not been connected.

You can first see if the plug-like indication on the computer is on, if not, it proves that the AC power is not connected at all, so it is equivalent to still using the battery, in this way, when the battery is insufficient, it is normal to press the switch indicator to flash and turn off automatically.

If the indicator light of the plug is on, then the problem may be related to the motherboard, you can reset it first. It is to unplug the alternating current first, unplug the battery, and then press and hold the switch for 10 seconds without power, and then release the switch, only connect the alternating current and then try to turn it on, which can generally be opened.

If you can't open it again, you can only consider sending it to the maintenance point to see. Good luck to the landlord!