M4400 - display problem ??

Yesterday, I put my M4400 into sleep mode as usual, then brought it home. When I switched it on at home, the backlight came on, but the screen remained blank. Caps lock still went on & off fine, and the drive light flickered occasionally. I left it on for 15 mins, but no change, so I put it back to sleep with a short press of the power button (went to sleep as usual), and tried again this morning. Same problem.

Held the power button down to fully switch off, removed power lead & battery, then tried again with power lead (no battery). Same problem. Connected external screen and did Fn-F8 to switch to external. Backlight goes off and external monitor reports "input not supported" (instead of "no input" before I pressed Fn-F8).

Held power button down to switch off. Unplugged. Removed both hard drives. Held power button down for 60secs as I've read on other forums. Plugged in, switched on (external monitor still connected), after maybe 10 secs I get a double-beep to indicate no bootable device present. Fn-F8 - this time the external monitor WORKS - I get a bootup-type text screen with a message about no bootable devices, F1 to retry boot, etc. THIS IS THE ONLY TIME THE DISPLAY HAS WORKED SINCE THE PROBLEM STARTED.

Since then, I've rebooted several times, removed and re-installed the hard drive, held the power button down several times, left it unplugged for 10 mins at a time, and I'm no longer getting the double-beep, and no longer getting anything at all on the external monitor.

Any ideas? It's really bizarre that the external screen worked once, and now won't work again. Also, why did I get the double beep once, but not again?

Could my motherboard be on the way out but not quite gone yet?

I have a service manual and am quite comfortable pulling apart as necessary.

Thanks guys for any help you can give.

Hardware:
M4400 15.4" RGBLED
Processor: T9600 2.8GHz
Video: onboard NVIDIA Quadro FX 770M
64GB Crucial SSD boot drive
2nd SATA HDD in caddy in modular drive bay
8GB RAM
Windows 7 Ultimate, no swap file

 

No one?

Ok, forget for now that I mentioned the external screen not always working, as I've got that working occasionally now. Let's just assume that the problem is as follows:

No display of any kind on LCD, but backlight works. No Dell splash screen on startup. Computer boots as normal.

I've read that this is likely to be the inverter ??

Could anything else cause this problem, or is it always the inverter?

 

Not an inverter issue if your backlight is working.

Does it work on an external display if you physically disconnect the internal display?

Otherwise, you are indeed probably facing a motherboard issue.

 

Does it work for getting into BIOS?

 

Fixed it!

Must have been a loose cable.

I opened it up and removed and reconnected both end of the main video cable (on the back of the LED screen and also on the motherboard) and it's now working fine.

I don't know what was causing the intermittent non-functioning on the external screen - bit strange that.

Thanks for the suggestions guys.

 

HERE IS SIMPLE SOLUTION I SHARE WITH EVERYONE...

The SolidWorks drivers are rigorously tested. Just go down the list to Dell, M4400...Then, when you get to SolidWorks version, choose 2012--you don't need Solidworks on your machine!

http://www.solidworks.com/sw/support/videocardtesting.html

Happy computing on your M4400!

- Don