My HP pavilion DV4 will turn on but not display anything. The screen remains black and the caps light/scroll lock buttons blink. Trying to figure out what it is if you can help please respond.

hp.com
the manual there those blink codes.
dv4 is only the prefix model number not full
full matters most and product ID.
all those failed now for bad CCFL back lamps. and more
take out the big battery (dropped out)
hold power button for 10second on AC power pack only.
get screen HP splash? and BIOS pages work?
get bios working first.
2008 PC, the CCFL laps die at 20,000 hours. 10hr/day used.
there are 7 blink codes
blinks codes changed on April 2015
so yours are old
and documented endlesslly at hp.com and asked more at their forum.
here

https://h30434.www3.hp.com:443/t5/Notebook-Boot-and-Lockup/HP-Laptop-Error-Blink-Codes/m-p/6142972


1=cpu
2=bios corrupt
3-memory fail ddr.
4- GPU graphic
5- main mobo problems.
6- BIOS checks fail, CMOS battery dead?
endless blinks no pattern is power pack bad or overload
wrong pack or huge battery shorted

Since you have graphics on an external monitor, the problem is the Video Cable, or inside the Display Assembly.

http://h10025.www1.hp.com/ewfrf/wc/product?product=3860431&lc=en&cc=us&dlc=en&lang=en&cc=us

This is a general example of a Video Cable, (Display Cable - HP), for an HP Pavilion DV4 series of Notebook PC,

http://www.ebay.com/itm/NEW-ORIGINAL-HP-PAVILION-DV4-LAPTOP-LCD-VIDEO-CABLE-DC02000IO00-486878-001-14-1-/281038275215?pt=US_Laptop_Screens_LCD_Panels&hash=item416f2fc28f

Mouse over to enlarge

The Video Cable connects to the motherboard in an area under the Keyboard, (About where the Fn key is), routes up along the motherboard, then routes up through the left Hinge, and into the Display Assembly.

From there it connects to the screen Inverter (Display Inverter -HP), and back of LCD screen.
It also connects to the LED backlight.

Either connections are loose, or the Video Cable (Display Cable) is damaged.
If the sheath of the cable shows apparent visual damage, so may be the tiny wires inside. (Stretched/Broken)

Connections CANNOT just be visually determined if they are loose.
You MUST physically check EACH connection.

Tightening connections does no good?
Perform a continuity test with a multimeter set to OHM's, on every wire in that Video Cable.

Have an assistant gently wiggle the cable in the middle, and check for an intermittent reading on the multimeter. Indicates broken wire if intermittent reading shows.

OR,

Take Video Cable to the nearest small computer store, and have the resident tech check it for continuity. Should just be a couple of bucks.

Use an ESD wrist strap, and connect it's alligator clip to a good ground source. (Electro Static Discharge)
Average cost is around $3 to $6.

Here is the download page for the free Service Manual, from HP Support,

http://h10025.www1.hp.com/ewfrf/wc/manualCategory?cc=us&dlc=en&lang=en&lc=en&product=3860431&

Scroll down, click on -
HP Pavilion dv4 Entertainment PC - Maintenance and Service Guide

Page 92 (PDF page at Top) for motherboard side of Video Cable (Display Cable - HP)

Page 80 for LCD screen, and Screen Inverter (Display Inverter - HP), and LED backlight.

Page 82 has false statements.

Remove the display assembly:

1. Locate the wireless antenna cable (1), and remove from path (2)

Should be;
Locate the DISPLAY CABLE (1), and remove from path (2)

2. Disconnect the wireless antenna cable from the system board (3)

Should be;
2. Disconnect the DISPLAY CABLE from the system board (3)

Somebody was on crack that day.

The wireless antenna cable information that follows, is correct.

Video Cable (Display Cable) is on the Left side.
Wireless Antenna wires are on the Right side.

For additional questions please post in a Comment.
Regards,
joecoolvette

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

Those blinks are codes from Bios.
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01732674&tmp_task=solveCategory&lc=en&dlc=en&cc=us&lang=en&product=3795310#N215
in this page you can check HP normal procedure
for what you are telling 1 blink is CPU failure.
If your laptop has warranty now is the time to call HP.

check out the blink codes here
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01443366&cc=us&dlc=en&lc=en&jumpid=reg_R1002_USEN

this model have 3 provlem one vga problem one processor problem & one bios last time i solve the problem vga

try to boot in f12 format then run windows after prompt.

Sounds like a loose connection if it used to work fine and problem starts after after you taken it apart.

I had the same problem with my hp pavilion dv4 1430 and to fix it I just took out the battery and unplugged it from the power adapter and pushed the power button and waited for a few minutes I put it all back together and started it up and the screen turns right back on.

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