Computer help forum: dv7-6165us won't power on

Just for information, I have taken apart, and replaced many motherboards in laptops, laptop screens, processors, heat sinks and fans. This is the first time with a quad-core and have came across this before. I have reballed alot of HP dv6000 and DV 9000 systems and have got them back up and running.
Specs for the laptop will follow discription of problem.
What I have is a HP DV7-6165US laptop which will not boot at all which is a friend of mine laptop. I believe the battery to be dead and it does not charge when plugged in. The only light that lughts when the ac adapter is plugged in is the light right on the side where the ac adapter does plug in, usually that light stays on steady when plugged in-- on this one it constantly flashes. Nothing lights up on the laptop itself when trying to power it on, the light where the adapter plugs in on the side just keeps flashing, it shows no other life at all.
What I have tried: A hard reset, Taking out all power connections including battery, holding down power button for a minute or more plug back in nothing changes. I've bought and tried a new stick of memory, I've taken it apart and bought a new internal ac jack still nothing changed, I've reseated the heatsink and processor, and now I just tried a new board (used $200) on ebay and put it in to find out I still have the same problem. The only thing I can think of that is left is the heatsink and fan assembly or the processor unless by chance I got a used motherboard from ebay that does not work (new board $400). Does anyone here have any idea if the processor being bad or heatsink that would cause this problem--as I said the only light is where the ac adapter plugs in flashes and keeps flashing when ac adapter is plugged in (normally the light around the ac adapter stays on steady when ac is plugged in) no other lights flash when pressing power button I also got the new processor and installed it same result. The light that is blinking is the one on the internal power jack where you plug the ac adapter in normally it stays on steady. Any help would be greatly appreciated TYVM!
dv7-6165us
Product Number LW460UA#ABA
2.4GHz/1.5GHz VISION A8 Technology from AMD with AMD Quad-Core A8-3500M Accelerated Processor
Microprocessor Cache 4MB L2 Cache
6GB DDR3 System Memory (2 DIMM) Maximum supported = 8GB
AMD Radeon HD 6750M s Switchable graphics
640GB (5400RPM)
SuperMulti DVD Burner
17.3" diagonal High Definition+ HP BrightView LED Display (1600 x 900)
Network Card Integrated 10/100/1000 Gigabit Ethernet LAN Wireless Connectivity •802.11b/g/n WLAN
•Beats Audio with the HP Triple Bass Reflex Subwoofer
Full-Size Island-Style Keyboard with Integrated Numeric Keypad
Touchpad supporting Multi-Touch gestures. With LED border accent light and On/Off button.
PC Card Slots External Ports •Digital Media Card Reader for Secure Digital and Multimedia cards •2 SuperSpeed USB 3.0 • 2 Universal Serial Bus (USB) 2.0 • 1 HDMI • 1 VGA (15-pin) • 1 RJ -45 (LAN) • 2 Headphone-out • 1 Microphone-in
Other Devices • HP TrueVision HD Webcam with integrated digital microphone • HP SimplePass with integrated fingerprint reader
Dimensions 16.38" (L) x 10.83" (W) x 1.24" (min H)/ 1.42" (max H)
Weight 6.65 lbs
Security •Kensington MicroSaver lock slot • Power-on password • Accepts 3rd party security lock devices
Power •120W AC Adapter
•9-Cell 100WHr Lithium-Ion Battery
What's In The Box HP TrueVision HD Webcam with integrated digital microphone
HP SimplePass with integrated fingerprint reader
Software Operating System: Genuine Windows 7 Home Premium (64-bit)