Chosen Solution
I have a Macbook Pro 13" Retina Late 2013 (A1502 802-3476-A) and it suffered liquid damage from the previous owner. I managed to clean up the corrosion on the board and it is able to successfully boot but only if I hold the power button down for 5-10 seconds. If I simply push the button normally, the fan will spin briefly and the machine will power off before the Apple logo shows up. When it does boot, the clockspeed of the CPU is locked to 0.8GHz and it will never go up to its proper 2.4GHz so it runs really slow. This is likely because the 5 second power-on is an SMC check bypass and its doing so as a protection measure. Apple Hardware Diagnostics comes up with no issues. I did observe corrosion around the ISL6259 (U7100) but I managed to clean it off, and since the computer is able to boot and charge the battery, I am assuming the chip itself is alright. I’ve been reading the schematics and saw some advise elsewhere that I should be checking the pins on the ISL6259 but since I’m new at this, I am not sure where to start. How would I know if there is a break in the trace? My continuity tests are coming up weird where I can touch two unrelated points such as pin 17 on the U7100 and any pin on the R7150 and it says there is continuity. And should I be checking for resistance, and if so, where? Things I have validated:
- G3Hot is fine (otherwise it wouldn’t power on) this far
- Pin 17 and 18 of ISL6259 U7100 give me 12.6V though I can touch them together and my continuity tester goes off (crappy tester perhaps?)
- Battery is charging fine, charger is fine
- SMC and NVRAM has been reset
- OS has been reinstalled
- All components have been plugged in, I have also removed the Trackpad/Keyboard connectors and attempted to boot to see if it makes a difference (it doesn’t) Sorry if this sounds all very amateurish, I decided to get this broken machine as a learning experience but right now I’m pretty stuck. Thanks! Edit April 20: @rany Seems to be a break between pin 18 of the ISL and its associated Capacito/Resistor/Test Pad. It’s going to be a challenge to reconnect this as the trace to the chip seems to be broken and I’ve never soldered something so small before. I am going to assume I might need to create a jumper between pin 18 and the test pad. Any tips on how to do this preferably without a hot air station?
Edit April 21: @rany So I achieved some success. I was able to attach the jumper to the ISL pin 18 and the test point without any shorts. It’s not pretty but it definitely works. My issue now is that the ISL gets extremely hot when I plug in the power (which is probably what burned the trace in the first place), I tested all the pins for shorts however it doesn’t seem like anything is shorted. The resistance between pin 17 and 18 measures at 4.3ohms.
First of all, well done getting so far! Second of all, VERY IMPORTANT - proper use of a multimeter: you are testing in continuity mode while your laptop is connected to a power source such as battery or charger or both. This is why you are hearing a beep however you touch the board. NEVER EVER test for continuity and resistance when the board is connected to a power source. ONLY test voltages when your board is connected to a power source (and avoid at all cost shorting components together when testing voltages, thus creating additional issues and adding variables). ALWAYS test resistance and continuity when the board is disconnected from ALL sources of power. You probably or may be have fried your multimeter already. Now regarding your board: properly test resistance between pins (17 and 18) and then between (27 and 28). What are the values you are getting - in Ohms? Why? Because pressing and holding the power button bypasses SMC over-current detection between AMON and BMON if I remember correctly. Specially that you mentioned corrosion, which means those lines are probably damaged. Otherwise like @reece said you have to use a known good keyboard and trackpad, making sure the trackpad itself of the flat cable are not corroded. But you can start by ruling out issues around the ISL. EDIT: @renegade_r got the board and indeed the jumper was badly made and the repair attempt caused some pins of the ISL to short together. It shows in the picture you posted. So we replaced the ISL, all the corroded components, and the LCD connector, and this is how it went: Upon arrival:
Before and after removing the ISL and neighboring components:
The LCD connector was heavily corroded and took some serious effort to clean:
Other components all over the board were corroded:
People shrug when I mention pro ultrasonic cleaning. Here’s an example of the difference it makes, and imagine that this same scrubbing happens even underneath the chips:
And the final result:
Try unplugging everything but the battery and fan, when you plug the charger in, does it boot up straight away? If so, see if it runs at normal speed (plugging in what is required). To get into SMC bypass you have to hold the power button, plug the charger in, then let go and press the power button again, if I remember correctly (haven’t done this in a while, but pretty sure just holding this button will not boot into this mode. Having to hold the keyboard power button to turn it on can indicate a bad keyboard, where the voltage is not dropping enough when you just press the power button quickly. Check WS_KBD_ONOFF_L whilst pressing the power button, if it is not dropping under 2V-2.5V, I would recommend trying a known working keyboard to check this out. Download ASD for your particular model and run a test on it, it will point out any sensor issues, if there is a problem with the logic board.
