introduction: Before you choose this solution, keep in mind, there are many problems that cause no backlight. For example the mosfet, coil and diode components may be broken. In this case the driver detects a failure (with the feedback resistor) and turns off. In my case everything was right. The microcontroller doesn't provide the PWM signal. But it took a long time to get this information. First I measured the signals on the board. Is the driver enabled? What is the input value of the PWM (S1 and S2) pin. I also checked (with the help of the data sheet) the mosfets, coils and diodes: Which pin of the driver is connected to the gate of what mosfet and what kind of function does it have? In the end I found out, that the external components are ok, so I began to make some tests with the driver! In the image you can see the little wire that put the 3.3 voltage as input for the pwm signal. The backlight turns on and the cinema display is alive again! the long story: After four years of using the backlight of...

I had the same problems. Backlight was gone or very low. The short story: I found out that the micro controller does not send the PWM signal to the LED driver. Very mysterious! I checked the LED driver components (Mosfett, diode), I read the data sheet to understand the function of the HV9982 (LED driver). In the end there was no hardware problem there. If I connected the computer the micro controller enabled the LED driver but "forget" so send the PWM signal, so the LEDs stayed off. Mmmm...maybe this is a software error or Apple wants to tell me to buy a new one? So I bridged the PWM input pins with a little wire connected to a 3.3 V pad (which I found about 1 cm around). Nice that die PWM output pins of the micro controller were bridged by 0 ohm resistors, so I could remove same and cut the connection from the micro controller. And then I got full backlight again. Of course I am not able to dim the backlight anymore.

I had the same problems. Backlight was gone or very low. The short story: I found out that the micro controller does not send the PWM signal to the LED driver. Very mysterious! I checked the LED driver components (Mosfett, diode), I read the data sheet to understand the function of the HV9982 (LED driver). In the end there was no hardware problem there. If I connected the computer the micro controller enabled the LED driver but "forget" so send the PWM signal, so the LEDs stayed off. Mmmm...maybe this is a software error or Apple wants to tell me to buy a new one? So I bridged the PWM input pins with a little wire connected to a 3.3 V pad (which I found about 1 cm around). Nice that die PWM output pins of the micro controller were bridged by 0 ohm resistors, so I could remove same and cut the connection from the micro controller. And then I got full backlight again. Of course I am not able to dim the backlight anymore.