Diode mode BGA continuity check

From LogiWiki - Your Wiki for all things Apple MacBook and iPhone related
Jump to navigation Jump to search

There are many cases when you do not have time to reball or resolder SMC or any other BGA chip but you need to check if there is continuity between IC and some line. In most ICs there is a diode between ground and data line. If you isolate the part of the circuit, you can see if you got 0.4..0.6 Voltage drop from ground to pin. Red probe on ground, as always.

Example:

820-00165, no backlight, PPBUS on backlight, no boosting.

  1. Disconnect LCD, Remove diode on pos. D7701 to isolate the circuit
    Diode7701.png

  2. Put red probe on ground, black probe on D7701 pin 2. As mentioned, OL means no continuity to IC.

Example 2:

Quarter spin 820-00165, U5110 is okay and PP3V3_S5_AVREF_SMC is also present/not shorted to ground.

Remove U5110 and check continuity same as mentioned above.