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820-2879 Issues

tlough75

tlough75

Member
So a customer of mine gave me a couple of 820-2879 boards to mess with and the first one works but has no backlight, the second one though seems to have more problems. It wasn't turning on at first so i removed it from the chassis to inspect it and found no real signs of liquid damage, and to measure PP3V42_G3H resistance to GND. That was measuring 220K so I assumed the MCP is ok. Well after I put the board back in it started up to the Apple logo and progress bar. After about half way the logo and progress bar slowly faded out to a white screen. My two questions are: Did I just witness the GPU or MCP die? Other question is, how would I be able to tell by measurements?
 
tlough75

tlough75

Member
Did a PRAM Reset 3 times and that cleared up the slow booting issue. Now boots into OS login in like 3.5 seconds. So it looks like I just needed to talk myself through this one.
 
tlough75

tlough75

Member
Actually they are both solved and working. I do have an 820-2530 that I need to maybe create a thread on. PP3V42 and PPBUS were .08 and no Magsafe light. Found pad under pin 5 of U6690 was corroded away so I placed a temporary solder bridge to chip and trace, now have chime and backlight but no image.
 
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