Power but no display

SOURCE: HP Pavilion dv4 not booting up, has blinking caps and scroll lock

Compaq and Hp are having issues with several models, My wife just got hers repaired free out of warranty. Go to copaqs website, look up your model and see if it is one they are offering free one time repairs on. Wife's computer was doing same thing, they replaced the motherboard. Took about 2 weeks round trip . Good luck

SOURCE: My laptop screen is black and caps lock and scroll key are flashing

That is a security configuration on HP Laptops, depending on the way they blink is the problem your machine has.

Here is the web page where this info is posted, in case you need more info, hope this helps you to determain.

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01443366&lc=en&dlc=en&cc=uk&lang=en&rule=26781&product=3816592
This document pertains to HP Notebook PCs with the HP Unified Extensible Firmware Interface (UEFI) beginning in late-2008. On startup, you may see a blank screen. If the diagnostic utilities detect a specific problem with hardware components, the fan turns on, but the screen remains blank. To help identify the cause of the problem, various LED lights on the keyboard blink a series of codes. The diagnostic utilities use the LEDs near the Num Lock or Caps Lock keys to blink a series of error codes. At the end of the series the blinking stops. The pattern of blinks will occur any time you attempt to start the computer until the error is resolved. Battery power LED blinks The Battery power LED indicates the condition of the power supply. When starting the computer, or when the computer is in operation, use the chart to identify the power condition. Battery Power LED Component Tested Error Condition Battery power LED off, and Caps Lock/Num Lock off Battery or AC Adapter AC adapter not connected or failure

Battery low charge or failure Battery power LED blinking Battery Insufficient charge on the battery When new computer is used for first time, the white LED light for the AC power connector blinks. Battery is still in "Shipping Mode", the light continues to blink even when AC power is connected.

To resolve, turn off notebook, connect AC power and allow battery to charge for at least 30 minutes, then start computer. LEDs near Caps Lock and Number Lock keys blink when starting notebook The LED lights near the Caps Lock and Num Lock keys will blink if an error is detected during the start up process. The LEDs will blink a number of times in a sequence and then stop. The number of blinks in the sequence indicates what component caused an error when it was being tested during start up. If the LEDs stop blinking and the computer does not start, you can press the power button again to repeat the tests. Count the number of blinks, and use the chart to identify the error condition. Knowing the number of blinks is helpful when you contact an HP support agent for technical help. Caps Lock/Num Lock LED Component Tested Error Condition LEDs blink 1 time CPU CPU not functional LEDs blink 2 times BIOS BIOS corruption failure LEDs blink 3 times Memory Module error not functional LEDs blink 4 times Graphics Graphics controller not functional LEDs blink 5 times System board General system board failure LEDs blink 6 times BIOS BIOS authentication failure