Hi, got this a2442 with a broken screen. Was working well only screen cracked and power button not functioning. The previous repair shop already opened it and cut the flex cable of the power/touchID button. I wanted to test with a powerbutton of a 16" a2485, looked like the same in the schematics. After connecting it and booting it kept saying "Keep pressing the power button to go to startup option". (The popup what you receive when the power button is been pressed during boot) But I wasn't pressing anything. I saw that I connected the cable the wrong way... I connected it upside down. After disconnecting and trying to start. The laptop starts with apple logo and In 1 sec it shuts down, then starts again and shutdown down. It does this 5 times and then gives apple support logo and does nothing...
I measured all pins on JT500 in diode mode, checking for a short nothing special. I had another a2442 so took the diode mode reading and came to the conclusion that pin 7 was higher.
JT500
Known working laptop
1. 0.0
2. 0.0
3. 0.518
4. 0.0
5. 0.687
6. 0.642
7. 0.556
8. 0.496
9. 0.638
10. 0.496
11. 0.0
12. 0.517
13. 0.0
14. 0.0
15. 0.542
16. 0542
Faulty laptops same but pin 7 was 0.679. Checked on that line and found a little black spot on UT540. Decided to change it of a donor board. After replacing. The Diode mode reading was 0.600 on pin 7 so thought close enough... But still the same issue!
Now I'm out of ideas... Please advice!! THXS
I measured all pins on JT500 in diode mode, checking for a short nothing special. I had another a2442 so took the diode mode reading and came to the conclusion that pin 7 was higher.
JT500
Known working laptop
1. 0.0
2. 0.0
3. 0.518
4. 0.0
5. 0.687
6. 0.642
7. 0.556
8. 0.496
9. 0.638
10. 0.496
11. 0.0
12. 0.517
13. 0.0
14. 0.0
15. 0.542
16. 0542
Faulty laptops same but pin 7 was 0.679. Checked on that line and found a little black spot on UT540. Decided to change it of a donor board. After replacing. The Diode mode reading was 0.600 on pin 7 so thought close enough... But still the same issue!
Now I'm out of ideas... Please advice!! THXS