[SOLVED]iMac 27" 2011 no backlight

[Dozer]

hi, i got this machine with no picture, dark screen.

now i replaced the grafik card, picture is there but after about 10min again dark screen and smelling
i found the inverter board a blown up ZD3, in the middle between the mosfets

i replaced the inverter board, picture is there but after half an hour smelling and dark screen.

inverter board again blown, this time ZD2.

no i still have 2 inverter boards. but i think if i replace it again will pass not long time and again it will be blown.

but i have no idea what could be the reason.

the power unit? or the screen? need a help please. any suggestion?

 

[Dozer]

no suggestions?

 

[Dozer]

No Title

 

[dukefawks]

Make sure to check for damage/shorts on the backlight LED cable first.
After that probably the usual LED strips inside the LCD. Completely rip apart the LCD, take out the 2 LED strips and reflow all LEDs and the 2 connectors. If this is the first time you will probably destroy the LCD so be prepared to buy a new one. Or find a cracked/scratched one to practice on first!

 

[Dozer]

thanks duke. i tryed now the next inverter and another lcd. now it is working over hours without problems. so you was right with the lcd inside. i offered the customer that used lcd and he is happy now. if i will have a lot of time i will dissasemble the faulty one to have a look, it looks like a lot of fuddely work
thanks for help what to check first.