So a little bit of backstory on this one I received an A2338 820-02020 in for repair again.
This is a device we previously repaired around 9 months ago for no power - in that instance we replaced one of the CD3217's (UF400) as it was burned out which fixed the problem.
Same device has come back in for repair again - we have opened it up and found that UF400 has exploded completely - also there is evidence that the client has taken the device elsewhere as I couldn't find the missing pieces of UF400, heatsink was bent and multiple screws were missing all over the place.
Anyhow back to the diagnosis and repair:
Replaced UF400 with a CD3217 from a donor board - board still stuck on 5V
Replaced UF400 with a brand new CD3217 - board still stuck on 5V
Proceeded to check voltages:
PPBUS_AON - 12V - seems too low to me but it's there
PP3V8_AON - 3.8V
PP3V3_S2 - 3.2v
PP5v_S2 - 5v
PP3v3_S2_UPC - 3.3v
PP1v25_S2 - 1.25v
PP3v3_UPC0_LDO - 3.3v
PP3v3_UPC1_LDO - 3.3v
PP1v5_UPC0_LDO_CORE - 1.5v
PP1v5_UPC1_LDO_CORE - 1.5v
These voltages were all tested with the board out of the case with just the charger connected to the topmost type c port (Closest to display)
Plugged the macbook into another and opened apple configurator - it isn't coming up at all so doesn't seem to be in DFU mode.
In terms of behaviour on the USB C Ammeter:
With Board out of case on its own:
Type C Port nearest display - 5V 0.26a then drops to 5V 0.05a
Other port - ammeter loops
With board installed in case and all parts connected:
Both Type C Ports - 5V 0.46A stable no looping.
This is a device we previously repaired around 9 months ago for no power - in that instance we replaced one of the CD3217's (UF400) as it was burned out which fixed the problem.
Same device has come back in for repair again - we have opened it up and found that UF400 has exploded completely - also there is evidence that the client has taken the device elsewhere as I couldn't find the missing pieces of UF400, heatsink was bent and multiple screws were missing all over the place.
Anyhow back to the diagnosis and repair:
Replaced UF400 with a CD3217 from a donor board - board still stuck on 5V
Replaced UF400 with a brand new CD3217 - board still stuck on 5V
Proceeded to check voltages:
PPBUS_AON - 12V - seems too low to me but it's there
PP3V8_AON - 3.8V
PP3V3_S2 - 3.2v
PP5v_S2 - 5v
PP3v3_S2_UPC - 3.3v
PP1v25_S2 - 1.25v
PP3v3_UPC0_LDO - 3.3v
PP3v3_UPC1_LDO - 3.3v
PP1v5_UPC0_LDO_CORE - 1.5v
PP1v5_UPC1_LDO_CORE - 1.5v
These voltages were all tested with the board out of the case with just the charger connected to the topmost type c port (Closest to display)
Plugged the macbook into another and opened apple configurator - it isn't coming up at all so doesn't seem to be in DFU mode.
In terms of behaviour on the USB C Ammeter:
With Board out of case on its own:
Type C Port nearest display - 5V 0.26a then drops to 5V 0.05a
Other port - ammeter loops
With board installed in case and all parts connected:
Both Type C Ports - 5V 0.46A stable no looping.
