iMac No Display, no 4th diagnostic led

HI,

could someone tell me where I can find pinout for espower pwb-iv49151t inverter board please ?

I need to test it as I've just receive replacement screen for my iMac and it's still dead.

symptoms :

-4th diagnostic led not on.

-when dp ribbon disconnected the fans go full blast.

-when all the cables are connected the internal screen is discovered as online by system info and starts with internal as main screen (4th led still off).

-when disconnected from inverter board screen is not discovered.

the Mac works fine with external display.

if anyone have any suggestions I'll be forever grateful.

Seb