tcampbell34
Member
Hello. I got a 820-00840 that was originally stuck on 5v. I had to replace both CD3215 chips and got 20v back and the board booted and it seemed to be working fine. Then I restarted it and tried to run apple diagnostics and during the test, the computer just turned off and would not turn back on. I immediately checked for a short on PPBUS and it was now shorted. I compared diode mode values on the large coils and found the short was on U7210. Replaced that and the short on PPBUS was gone but now when I try to turn it on again, it does not seem to post. It seems to be taking the correct amps for a working board (300-600ma), but has no USB activity or cap lock reaction. All the rails seem to be working correctly, but I did find that PP3V3_S0 is showing a low diode mode reading compared to a good board. Diode mode reading is about .050 but it does have 3.3v still. I tried to inject up to 4v into the line but nothing really gets hot. I am wondering if the low diode mode reading is a indication of an issue even though the voltage is present. Should I just start removing things connected to PP3V3_S0 until the diode mode reading goes back to normal?
