[SOLVED]820-4924 backlight issue

[laptopcity]

Hi , ive got an 820-4924 with a backlight problem
q7700 is not being told to turn on , pin 3 12.4v pin 4 12.5v pin 1,2,5 and 6 0v,
r7731 and r7732 lcdbklt fb measure fine also tracks are good
no short either side of d7710
at u7700 pin5 5v pin18 5V pin 17 bklt en 3.3v
I2C_BKLT_SCL and I2C_BKLT_SDA tracks are fine from screen connector to u7700 , pullup resistors r7753 5.13v and r7752 4.86v
no signs of a short, changed u7700, q7700, all the resistors i have mentioned just incase plus q7701 just for good measure and still no joy, am i missing something, also its good working screen and have 5v on l8300

 

[dukefawks]

Is there an image? Is it a known good 2015 LCD? SMC_LID high? Connector inspected for damage? Any history?

 

[laptopcity]

yes has image on screen, lcd 100% good for 2105, smc_lid is 3.3V lcd connector looks ok but would it be worth changing just incase ?. history of laptop is we changed the screen 2 - 3 months ago due to laptop being dropped but apart from that no water damage or anything like that, apparently just didnt work one day

 

[dukefawks]

PRAM reset done? If you are relying on the screen being 3 months old and thus must be ok then first thing to try is another LCD.

 

[laptopcity]

out of complete desperation i changed the lcd connector even though it looked fine and the feedback lines measured ok and now i have backlight