I got a tricky one today in the form of a macbook air A1466 820-00165-A that will recognize the charger and turn the light green then back to orange and the fan will spin constantly, but the system won't power on. The screen never turns on, it doesn't make the bong noise it's supposed to, and pressing the power button doesn't do anything. When I took the board out to visibly inspect it I only found one spot of corrosion on the bios IC. I pulled the chip, cleaned it and the area with IPA and put fresh solder on both and put the bios chip back on, but when I went to test it again it still does the same thing as before. The only damage to the area is the gnd pin for the bios chip is gone. As I write this I realized I never rebuilt that pad because I figured it wouldn't matter since the big gnd on the bottom of the chip was intact. The corrosion was mostly on pins 3,4,7,8 and nowhere else on the board. I forgot to take a picture unfortunately of the affected area.
I measured the current draw from the charger and I'm getting 20v with 0.5A initially then it occasionally will dip to 0.3A after about a minute then after another minute it will jump back to 0.5A. It doesn't always fluctuate and when it does it always goes back to 0.5A. Pressing the power button also doesn't change how much power it's drawing from the wall.
I checked the bios chip with my oscilloscope and found that I had only flat 3.3V readings on all pins except for the spi_clk line where I had nothing at all. I checked the pins on the clock generator IC and I believe I had all the correct clock signals coming out of it. I had 24mhz signals present on all the pins that I believe I should according to the board schematic. I haven't tried replacing the IC yet. I'm out and waiting on some new ones to be delivered tomorrow. From reading another post on badcaps I did check all the resistors in line with the spi_clk and all of them tested fine in circuit (the 15ohm and 43ohm ones read spot on so I didn't see any reason to take them out of circuit to test).
I did try a working bios chip that was already programmed off another board I had with a dead cpu and nothing changed. I also did the basic short hunting and everything tested fine and when checking the resistance of the inductors to gnd they all read normal. Nothing high and nothing low.
I did take voltage measurements at all the large inductors as well
L7310: 1.8V
L7320: 1.8V
L7630: 1.06V
L7430: 1.2V
L7560: 3.3V
L7520: 5V
L7130: 8.5V
L3095: 0V
L7701: 0V
I also checked both fuses and they weren't blown and both had 8.58V present. In some other spots I was able to read 12V, but never any 20V other than on the charger board. I'm assuming the 20v rail is fine though since I have lower voltages present even when the battery is unplugged. In general all the testing I've done has been with the battery disconnected.
Other than waiting on more clock gen IC's to come in tomorrow I'm kinda at a loss for were to go from here since everything else at first glance and testing looks to be ok. There's plenty more I probably could have tested, but I didn't feel like sticking around work any later than closing.
Side note tangent I don't know how these macbooks always get one tiny little drop of water inside them with no signs of water anywhere else in or outside the laptops. I swear they make these boards out of sponges.
I measured the current draw from the charger and I'm getting 20v with 0.5A initially then it occasionally will dip to 0.3A after about a minute then after another minute it will jump back to 0.5A. It doesn't always fluctuate and when it does it always goes back to 0.5A. Pressing the power button also doesn't change how much power it's drawing from the wall.
I checked the bios chip with my oscilloscope and found that I had only flat 3.3V readings on all pins except for the spi_clk line where I had nothing at all. I checked the pins on the clock generator IC and I believe I had all the correct clock signals coming out of it. I had 24mhz signals present on all the pins that I believe I should according to the board schematic. I haven't tried replacing the IC yet. I'm out and waiting on some new ones to be delivered tomorrow. From reading another post on badcaps I did check all the resistors in line with the spi_clk and all of them tested fine in circuit (the 15ohm and 43ohm ones read spot on so I didn't see any reason to take them out of circuit to test).
I did try a working bios chip that was already programmed off another board I had with a dead cpu and nothing changed. I also did the basic short hunting and everything tested fine and when checking the resistance of the inductors to gnd they all read normal. Nothing high and nothing low.
I did take voltage measurements at all the large inductors as well
L7310: 1.8V
L7320: 1.8V
L7630: 1.06V
L7430: 1.2V
L7560: 3.3V
L7520: 5V
L7130: 8.5V
L3095: 0V
L7701: 0V
I also checked both fuses and they weren't blown and both had 8.58V present. In some other spots I was able to read 12V, but never any 20V other than on the charger board. I'm assuming the 20v rail is fine though since I have lower voltages present even when the battery is unplugged. In general all the testing I've done has been with the battery disconnected.
Other than waiting on more clock gen IC's to come in tomorrow I'm kinda at a loss for were to go from here since everything else at first glance and testing looks to be ok. There's plenty more I probably could have tested, but I didn't feel like sticking around work any later than closing.
Side note tangent I don't know how these macbooks always get one tiny little drop of water inside them with no signs of water anywhere else in or outside the laptops. I swear they make these boards out of sponges.
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