Voltages of pins on logic board where inverter cable hooks up.

This question is old, but since I have just had similar issue and repaired it, I feel I must contribute.

My MacBook is A1181 Penryn, the inverter is connected via 4-pin connector with the following voltages: pin1 (right side): 12V, pin2 : ground, pin3: 5V, pin4 (left side): 3.3V.

You can find full picture of the board here:

http://www.google.ba/imgres?imgurl=http:...

I had an issue of flickering backlight at certain screen positions. I replaced the inverter cable (one of the wires was pinched, but it was not visible until I removed protective tape). A month after that, the backlight was gone, so I ordered CCFL bulb (with wires already soldered). It was painstaking procedure, this LCD is not designed for bulb replacement, so I wonder that it worked!

Anyway, during reassembly and testing, I accidentally shortened board and got a puff of smoke. Laptop worked, but backlight was gone again, grrrr. I tested voltages and found out that 12V from inverter connector was gone. There are four resistors underneath the connectors and another four under first four that are actually zero ohm resistors, and they burn if overcurrent is applied. Picture of that portion here:

https://docs.google.com/file/d/0B9ITSlcv...

The board does not have fuses, so these serve as protection. The 12V power comes from the stabilizer on the right of the golden thing to the right of the connector. 12V exists there even if laptop is off. I tought first to bring 12V from there, but the solution was actually simpler. Since the zero ohm resistor for pin 1 was burned, I used small soldering iron and very, very carefully applied small amount of solder to connect 2 pins of the burned out resistor. And, voila, there was 12V at pin 1! Turned on MacBook and the backlight is back!

There is also very useful video of similar procedure for 2009 MacBook board.

http://www.youtube.com/watch?v=YQxCe0iZ9...

To summarize: if you have backlight problems like no backlight at certain positions of screen panel, try in this order:

1. Reset SMC - disconnect power, remove battery and press and hold power button for more than 5 seconds.

2. Use guide here on IFixit to dismantle MacBook (replace inverter guide), but first check inverter cable. It most probably has one wire broken.

3. If not the cable, then replace inverter using that guide.

If there is no backlight at all, try all this, but first check voltages at inverter connector. It may then be CCFL bulb (very tiny neon light), but do CCFL replacement only if you like to do stuff like that. It will take you 2-3 hours and a lot of stress, but it may also relieve you of stress!

Even if you fail replacing the bulb and destroy the LCD, you can always purchase replacement LCD screen on ebay.