Chosen Solution
I have a 15" Retina Display that got some moisture in it (visible as bright spots in lower corners of screen) and apparently shorted the backlight, causing the backlight fuse on the logic board to blow. I subsequently put the display clamshell in a plastic bag, along w/ 2 large desiccant bags. That was several days ago. When I have the logic board replaced or repaired, is there any way I can check the display first to make sure it’s not going to pop the fuse again? Thanks, Fred EDIT: I have been able to get the fuse replaced (thanks, James!), but found that the backlight short was still present. After another fuse replacement due to popping the first, I’d like to know if there’s any way w/ a multimeter (perhaps on the display cable MLB connection?) or other tool to check to see if/when I get the short fixed. Related question: Since the Retina Display is essentially impenetrable as far as repairs go, can anyone offer tips on how to get any remaining moisture (from isopropyl alcohol) out of it and fix the short?
Sadly, it sounds like your display has gone. Time to replace the part. While its possible moisture is still present water alone is not the enemy as many people think! You could dip your system is distilled water wait a day or two after leaving it in the sun to warm and power it up! I don’t recommend you try this though ;-} Its the stuff in the water that kills you. The corrosion caused by the ionic action of the salts and other contaminants in the water likely has shorted the circuit so waiting any longer most likely won’t change things here. Sorry ;-{
Firstly never turn it on again or bother replacing the fuse without finding out if the short is fixed. Which board is this, is this 820-3332-A or a newer one? You tell if the short has gone away by putting your mulitmeter into ohms/resistance measuring, or diode mode. Put the red probe on ground, being the metal around the screwholes that hold the board into the machine, and the black probe on where backlight would be present. I like to grab the huge chunks of the ceramic caps right next to the backlight circuit. if you tell me which board you have I can tell you where to measure. Right now you have no idea if the short to ground is in the board, the screen, the LCD connector, or the screen cable. Also let me know if you have an old piece of junk PC you don’t mind blowing up that I will explain to you how to turn into a short finder so you don’t have to spend $1000+ on an infrared camera & lab power supply. Near the CPU on a PC motherboard you will see some transistors, one of which supplying something between 900 mv to 2v to the CPU. Solder a piece of wire to where you measure this voltage,and we’re going to attach the other end of the wire to the backlight power rail of the board if it IS shorted to ground. Then we attach the ground of the lenovo to the ground of the laptop, and turn the old clunker computer on. So let’’s say you attached the 1.7v from the old comp to the backlight rail on the board, you SHOULD see 1.7v on the logic board where backlight power would be would be, but something is shorting backlight power to ground, so that power will go to ground. Now since you attached the ground of the old computer to the ground of the board, that 1.7v will have a DIRECT path to ground through the shorted component. That shorted component will get very hot and you will know exactly what to remove/replace. The only circumstance under which nothing will get hot is if the short is inside the LCD connector. The LCD connector is just bare metal and will not get hot. Update
This is backlight. Measure from here to ground, red probe on ground, black probe on the top of this capacitor here in diode mode on your multimeter. What do you get?
