I'm familiar with electronics (extremely familiar with through the hole), just never dove into SMD repair until now, but I feel that I'm not doing a bad job of it so far, it's the troubleshooting I need help with.
I was given a MacBook Pro A1398 EMC 2512 (motherboard 820-3332) that had water damage. Specifically looks like the damage was to the backlight portion of the board (see attached). This was verified when I was unable to play with the brightness setting on the macbook without the light going out completely. After a few weeks sitting at my desk, I powered the Mac up and now there's no backlight regardless of where the brightness is set at.
I took it apart, cleaned the corrosion off, and verified that the 5 output caps on the board were not shorted, also verified the P-fuse still had continuity across the chip. I also took the LED backlight driver off the board and found the ground pin had significant discoloration on the outside ground pin.
None of the other components look suspicious (burnt or cracked), so I assume the 24 pin driver chip has gone bad. So I have a few questions:
I had a 3rd party sales site confirm the VM06AL is the correct chip, handy site to keep around: https://beetstech.com/apple-device-lookup
*2nd edit*
After watching several videos, I've learned more about backlight drivers and backlight driver circuitry than I could ever hope for. While a few more components *could* be at fault here, I still suspect the chip was bad, but now I know what to test and look for when I get the replacement installed. For anyone wanting to get to this point, there's an unnamed fellow on YT who explains backlight drivers really well and would highly recommend watching his DC to DC boost circuit simplified video. Easy to find.
I was given a MacBook Pro A1398 EMC 2512 (motherboard 820-3332) that had water damage. Specifically looks like the damage was to the backlight portion of the board (see attached). This was verified when I was unable to play with the brightness setting on the macbook without the light going out completely. After a few weeks sitting at my desk, I powered the Mac up and now there's no backlight regardless of where the brightness is set at.
I took it apart, cleaned the corrosion off, and verified that the 5 output caps on the board were not shorted, also verified the P-fuse still had continuity across the chip. I also took the LED backlight driver off the board and found the ground pin had significant discoloration on the outside ground pin.
None of the other components look suspicious (burnt or cracked), so I assume the 24 pin driver chip has gone bad. So I have a few questions:
Is there a way to test this chip? Or would the assumption of a bad chip be the next troubleshooting step?The chip in the image is a VM23AC. Google didn't return much, however if I search for LP8545, several different chips come up - one of which is a VM06AL, which I have ordered. Is this a suitable replacement?(The schematic referred to the chip as a LP8555, but it was a BGA chip, the original was not, but after some googling, it seems this one uses an LP8545)- Is there a way to test this backlight without completely reassembling the laptop?
- I found schematics for a 820-3332-A motherboard, I could not find a plain 820-3332 schematic (without the "A"), do they even exist? Or does everyone use the "A" revision schematic and figure out the differences?
I had a 3rd party sales site confirm the VM06AL is the correct chip, handy site to keep around: https://beetstech.com/apple-device-lookup
*2nd edit*
After watching several videos, I've learned more about backlight drivers and backlight driver circuitry than I could ever hope for. While a few more components *could* be at fault here, I still suspect the chip was bad, but now I know what to test and look for when I get the replacement installed. For anyone wanting to get to this point, there's an unnamed fellow on YT who explains backlight drivers really well and would highly recommend watching his DC to DC boost circuit simplified video. Easy to find.
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