Senthila Madiwanan asks:
My laptop model is Compaq Presario CQ40. It’s up running. I can hear the sound, but the screen is blank.
I tried the unplug power, remove battery, hold ON button for 60 seconds, then plug in everything and try rebooting, but it isn’t working either! Instead I can see the lights of the caps lock button & number lock button blinking simultaneously.
Any idea? PLEASE 
Browser: Chrome 20
System: Windows 7 Ultimum
Tagged: black screen, computer hardware, laptop, laptop screen
System: Windows 7 Ultimum
Tagged: black screen, computer hardware, laptop, laptop screen
13 Answers -
Susendeep Dutta
July 3, 2012Try entering into safe mode by pressing F8 button while booting your PC.Have you tried cleaning the RAM and resetting it?
If you recently update your graphics drivers then it might be the culprit behind it.
ha14
July 3, 2012This document pertains to HP Notebook PCs with the HP Unified Extensible Firmware Interface (UEFI) beginning in late-2008.
http://h10010.www1.hp.com/ewfrf/wc/document?lc=en&dlc=en&cc=us&docname=c01443366&product=3752104
check if the laptop is not configured to use mainly external screen?
Oron
July 3, 2012It could be that your internal display (i.e. your screen) is switched off. The switch is at the base of the screen on the left, approx. 1 inch from the edge.
Also, the laptop could be in “presentation mode” where the display is diverted only to the external screen/projector connector. You can switch mode by pressing the [Fn] key and simoultaneously the relevant Function key (F4?). You may need to press more than once as the system goes through the various permutations: internal screen only, external, both…
Dalsan
July 3, 2012Are you able to see the Compaq logo when turning on your laptop? If not, then there might be a problem with the screen or the connectisomewhereons in the laptop to the display. If at all possible, see if you can connect an external display, either tv or monitor, to see if it still displays. If it does, then the built in video card and drivers are working, and the screen or somewhere in between the motherboard and display.
*or the connection somewhere in the laptop.
*motherboard and display is damaged.
Sorry, my phone was acting up.
July 4, 2012Matthew Glaman
July 4, 2012I had a laptop that took a “little” bump once. The display cable came loose at its connection to the motherboard. I just had to take a few things apart and press it back in.
Compaq should have a guide on its product support page on how to take apart your laptop.
ferdinan Sitohang
July 4, 2012There are 3 options for this, First is the display screen is broken, two is your internal VGA is broken, Third is there is some shorting in the circuit. All of that are the common cause of the problem. Thanks. Hopefully It will help. The better way i think is to bring it to the hp service center.
Scott
July 4, 2012To troubleshoot if it’s the display try connecting a VGA cable to the laptop and run it to a monitor. If it produces a good picture on the monitor, you know the video adapter is working. Replace the laptop display or, the inverter board first.
If you don’t get any image from the laptop, it’s either the graphics card or an integrated graphics chip on the motherboard.If this the case, you may consider selling it off as parts!
Reuben Walker
July 4, 2012As Dalsan pointed out, it could be a hardware problem.
From a computer repair technician, I would say it’s either the mainboard (which includes graphics on laptops), the monitor, or the connection in between. (Which would probably require replacing one of those two anyway.)
I would try with an external monitor, and if that didn’t do it, I would say it was a write off. Unless the laptop is fairly new, a new one is probably the best way to go.
Yea, I agree, definitely try connecting it to an external display if you have one.
July 5, 2012Tony Batty
August 25, 2012OK, here is a simple test that you need to do to first to really ensure that your laptop is working, most, if not all laptops come with a VGA port out, if you have a secondary monitor for say a desktop system, plug the cable from the vga cable to the port on your laptop and turn on your laptop and the monitor too, it should automatically pick up the monitor, or you can try this sequence of buttons to bring it up the monitor online
Function (Fn) + F4 to toggle between screens, if you have you monitor come on, and the screen still not showing you may have a more serious problem, like the cable inside probably damaged. which will require a professional to look at it for you.
Hope this helps.
Vinita
September 5, 2012I have same problem with same compaq with windows 7 ultimate. When I turn my notebook upside down, I see operating system running properly and I see very very dull desktop. I also tried same way but no solution found yet. Looking for better solution.
ali
September 20, 2012i can see the compaq logo very dimly what can i do urgentl
Jim Chambers
October 13, 2012If you see a very dim display in bright light, your backlight or its power supply has failed. Or the wire from motherboard to lid via the hinge has broken.
Galey
October 16, 2012Please follow this link
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01732674&tmp_task=solveCategory&lc=en&dlc=en&cc=us&tool=&query=CQ40-107AU&product=3786474#N589