HP-Compaq HP 6720S starts with black screen

Hi members,

Hp 6720s- platform: DDD UMA 6050A2137901-MB-A03

When started, fan spins continuously but no display on screen and external monitor.

Current reading : 0.003-0.48 and stopped at 0.68

Steps made :

Replaced ram, and cpu, with known good working ones, same problem.
Flashed bios, reflowed GPU for test purpose to no avail.

Tested mobo :
-CPU voltages :
Vcc_Core :+1.12V
VCCP : +1.18V
+V1.5S : +1.7V a little high
H_Pwrgd : +1.18V
H_Cpurst# :+ 1.8V

GPU voltages : +1.18V; +1.44V; +2.08V

All other voltages are present and measured good except :

-At CN17 (lvds connector) :
+V3A(pins 18-19-20) is missing due to "LVDS_VDD_EN" absent.
LVDSA_DATA pins signals are also absent.

-Bios (soic8) pins 1 and 2 always 3.54v strange !!!

Please advise as where to dig further ! Bios, I/O or other component