Laptop screen lights up, but no image. External monitor shows image

If the Video Controller fails, the screen will stay black when the rest of the computer runs as it should. To test this, look to the side of the computer and locate the external Monitor attachment. It is a nine pin male outlet. Take a regular computer monitor and attach it to the connection and turn on the computer. If the Monitor acts like your normal LCD screen, then the main LCD screen is bad. If Neither the Monitor or LCD works, then the Video portion of the computer may be defective.

I suspect it may be a problem with the video cable coming from the convertible tablet, up through the hinged support for the LCD screen, AND/OR the screen Inverter.

I would like you to connect a VGA monitor, to the VGA port on the back of the convertible tablet. The VGA monitor will now be an External Monitor.

[ Looking at the rear of the convertible tablet, start at the Left side.
Vent, USB port, Monitor port. The Monitor port is the VGA port ]

The VGA monitor can be a CRT type, (Looks like a small TV), or a flat LCD screen monitor with a VGA cable.

Notebook OFF, monitor OFF, connect the VGA monitor to the M275's VGA connector. (Port)
Turn the monitor on. If a CRT type, allow it to warm up.

Turn the notebook on.
By the factory default settings, whatever is shown on the convertible tablet's internal monitor, should now be shown on the external monitor.
(VGA monitor)

If not, press, and hold down on the Fn key (On the bottom row of the Keyboard, all the way to the Left), and tap once on the F3 key.
(Top row of Function keys. The F3 key is the Display Toggle-Over Key )

No graphics shown on the external monitor? Hold down on the Fn key again, and tap the F3 key again.
There are at least three options available;

1) Convertible tablet's internal monitor - ONLY
2) Convertible tablet, AND external monitor
3) External monitor - ONLY

If graphics are fine on the external monitor, you have a problem with the video cable, and/or the screen Inverter. At this time we will bypass the LCD screen, and come back to it.

At the bottom/middle of the tablet's LCD screen, is the Hinge. The Hinge Cover is 'T shaped', and has one single Philips screw holding it on.
If you remove the screw, and the Hinge Cover, you will see two wire harnesses.
One Black, the other White.

See that these two cables are plugged in tightly to the connector.

After checking this step come back in a Comment, and state your findings.

Regards,
joecoolvette

[ Additionally;
Here is the Service Manual (Free) for the Gateway M275 Convertible Tablet,

http://www.tim.id.au/blog/tims-laptop-service-manuals/#toc-gateway

Where it states - Gateway 400, go down to the second line, and across to M275. Left-click on M275.
This is a PDF file. It may take up to 30 seconds before the first page comes up.

Dead Laptop?

Try firstly removing the laptop's battery as it may be at a critical voltage and the system will not start because of it. Plug in your ac adaptor and monitor what happens. Does the power light illuminate? If it does it should then boot up, if it doesn't, try a known good ac adaptor before going any further.
If the adaptor is fine then you have a mother board fault and should contact a dealer/repairer for further advice.
Hope this helps.

Then the screen has failed, though that would be obvious.

You have identified your problem/fault by plugging in an external monitor and the image is OK. This proves the video card is OK and the fault could be the inverter or most likely the CCFL lamp.
The flickering screen indicated the CCFL lamp is faulty, it is a mini fluro tube which provides the back-light to the LCD. The inverter supplies high voltage to the CCFL lamp. It could be faulty and it is easier to replace.
For service, parts and DIY info check out LCD Parts - use this link to their WEB site : -
www.lcdparts.net

If an external monitor showed graphics, then there is nothing wrong with your Graphics 'chip'.

{'Chip' is a slang term for IC. Integrated Circuit.

The Integrated Circuit for graphics is a GPU. Graphics Processing Unit. Your laptop uses the Nvidia GeForce G0 FX5200 GPU.

Your laptop like many others, does not have a graphics adapter card. It has Integrated Graphics. Another term is 'OnBoard'.
The graphics chip is on the board.
Motherboard.
There is no graphics adapter card to remove, and replace}

Some areas you may wish to address:

1.The Native Resolution is 1400 X 1050. What does it state in Display Properties?
(Right-click on any empty area of your desktop screen.
Click on Properties at the bottom of the list.
Click on the Settings tab)

2.There are known issues with the CMI display cable. Observe the display cable. Look at the letter/numbers under the barcode. Does it start with CMI?

3.There have been known issues with the connectors on digitizer cable
http://www.irisvista.com/tech/laptops/ToshibaM200/Portege_M200_digitizer_2.htm
(The above is for reference to the digitizer cable identification)

When you connect a data projector or external monitor to the external video port on the laptop, power up the data projector or external monitor first then the laptop. The video info will automatically divert to the data projector/external monitor automatically.
If you have already had powered up the laptop first, most laptops will allow you to toggle between the LCD screen and the external video port by pressing the Fn key plus one of the Function keys, this key will have a screen/laptop symbol.

Same thing for me 17 months old and normal usage

Look a the screen real close, if you see a faint dark version of the image, this could be a backlight issue, otherwise a screen cable or a logic board issue. Backlight repairs are somewhat difficult. As much as I would like to be able to tell you a quickfix that will solve backlight the problem, it's a pretty arduous repair that requires 1-2 hours for a trained person. It's feasible to do it yourself if you're tech savy, but you'll most likely have to google for guides that show you exactly how to replace the backlight step by step. Check on how to take the screen apart and make sure inverter is still connected properly. If so, you have a backlight issue. I work for Computer Repair NYC and i have to fix this problem a lot, it's so easy to break the lightbulb in the process.