My computer screne keeps going black.I shut it off

Hello there
You dont say which machine you have but a common problem is they are set for the WRONG input,
Have you checked using the 'onscreen' menu,of the monitor that you are looking at the right INPUT ???? D-sub is the 15 pin video cable input from your computer to the monitor. .It will go dark if you are not supplying a signal on that input.

You didn't mention what make and model you have - but this seems to be a graphics card issue. Many (HP laptops a few years ago in particular) developed "Cold" solder joints on the motherboard at the graphics card. When the computer heats up, the connection is lost, when it cools back down, the connection resumes. Usually requires a professional repair - either by attempting to "reflow" the solder, or replacing the motherboard in its entirety. Might be more cost effective to consider replacing the computer.

Sounds to me as though the backlight has gone faulty on your screen. It will need to be repaired or replaced I am afraid.

Huh? D-Sub is a connector? If you plug an external monitor into it the laptop is probably designed to shut of the internal screen. If this is not what you mean please get someone who can write a functional English sentence to clarify your meaning.

It sounds like you have not selected the correct INPUT to the device.OR not connected the cable correcty to the input.

Check your user manual for the device.

check your ohm load on the sub and see if your amp can do the same, That is why every time it shuts off into protection mode. Check your gain level on the amp to this is not a volume knob for your amp, It is to get both the amp and cd player on the same page. Hope this was helpfull

Most likely the TV has a power supply related problem. It's possible that it maybe a bad capacitor or transformer on the power supply board. The most common thing to go out is the circuit board that supply power to the screen. Commonly called a Backlight Inverter Board.
But, I can't say it's 100% the problem because I can't actually look at the tv over the internet.

If by chance the TV is still under warranty, go that route.
If not under warranty and If you have some electronic experience, if you can find and purchase a Service Manual over the internet; It will help you diagnose the source of the problem and fix it by soldering in the new part. The Service Manual will give you circuit diagrams, test points, and part# lists. Usually, cost under $20. And most cases the new part cost less than $15.

I hope I shed some light on the subject for you.

put someone else's simcard turn it on then off put your sim card in and turn it on that how i fixed mine

This is probably a back light problem. Take a bright flashlight and while the monitor is on, point it at the LCD and try different angles, etc. If you can see an image, it is the back light, probably the back light voltage converter unit in the lcd. It could also be the back light bulbs.

If you don't see an image with the flash light, then it could be the main logic board.

ort11