Technical Support A2289 820-01987 20V 0.1AMP - 0.9 AMP need help

[alfredposadas09]

the first issue is stuck at 5v.... I check PP3V3_G3H and it was shorted line i found q7680 is shorted so i replace the dual mosfet and the short is gone.. I have 20v now and 0.1amp - 0.9amp and i am having 20v on the fuse PPBUS_G3H @ F7000, still no bootup no fan spin.. i dont have PV5G3S_VSW ..

voltages and diode
PP3V3_G3H= 3.3volts & resistance = 3.6k ohms
PV5G3S_VSW =0v & resistance = 3.7k ohms << suspicious since missing voltage
PPBUS_G3H = 20v both side of the fuse
................................................
upon checking on CPU coils I found that PP0V95_S0_CPUVCCIO_REG_R L8102 reading is too low i reference on flexbv via diode mode the correct value is 0.124v diode but i am only getting 0.043...
U8110 generated the PP0V95_S0_CPUVCCIO_REG_R and its vin supply is PP5V_G3S_CPUREG_MISC << Maybe this was the reason why I am not getting 5v? is that possible? pls help me

 

[Admin]

the first issue is stuck at 5v.... I check PP3V3_G3H and it was shorted line i found q7680 is shorted so i replace the dual mosfet and the short is gone.. I have 20v now and 0.1amp - 0.9amp and i am having 20v on the fuse PPBUS_G3H @ F7000, still no bootup no fan spin.. i dont have PV5G3S_VSW ..

voltages and diode
PP3V3_G3H= 3.3volts & resistance = 3.6k ohms
PV5G3S_VSW =0v & resistance = 3.7k ohms << suspicious since missing voltage
PPBUS_G3H = 20v both side of the fuse
................................................
upon checking on CPU coils I found that PP0V95_S0_CPUVCCIO_REG_R L8102 reading is too low i reference on flexbv via diode mode the correct value is 0.124v diode but i am only getting 0.043...
U8110 generated the PP0V95_S0_CPUVCCIO_REG_R and its vin supply is PP5V_G3S_CPUREG_MISC << Maybe this was the reason why I am not getting 5v? is that possible? pls help me

Schematic - X1782 MLB - 820-01987 - 820-01987-06 Schematic

X1782 MLB - 820-01987 - 820-01987-06 Schematic

dr-bios.com

Based on the issue you described, it seems like you are dealing with a charging circuit and power rail problem on the A2289 (820-01987) logic board. Here’s a breakdown of the key points and next steps:

1. PP3V3_G3H Short and Q7680 Replacement:
   • You've correctly identified and replaced Q7680, clearing the short on PP3V3_G3H, and you now have 20V input and 0.1–0.9A on the USB-C ammeter. That's a good sign, but the fact that there is no fan spin or boot indicates there may still be missing power rails or other circuit issues.
2. PV5G3S_VSW:
   • You noted that you are missing the 5V rail PV5G3S_VSW, which is indeed suspicious. This rail is crucial for powering various parts of the system, and the missing voltage could be due to a fault in the buck converter or its associated components.
   • You mentioned that U8110 is responsible for generating PP0V95_S0_CPUVCCIO_REG_R, which in turn is related to PP5V_G3S_CPUREG_MISC. If PP5V_G3S is missing, it could indeed be the reason why the 5V rail is absent.
3. Checking U7000 (CD3215 Controllers) and U7650 (5V/3V Power Supply IC):
   • Since PP5V_G3S is not present, check U7000 and U7650. U7650 is responsible for generating the 5V and 3.3V power rails. Ensure that the EN (enable) signals and inputs to these ICs are working correctly.
   • Measure the voltages on the important pins of U7650 and see if any of its associated components are damaged.
4. Diode Mode Measurement on PP0V95_S0_CPUVCCIO_REG_R:
   • You’ve identified a low diode reading (0.043V instead of 0.124V) on PP0V95_S0_CPUVCCIO_REG_R. This low reading suggests a possible short to ground or a low resistance path on that line. It could be related to a faulty U8110 or a nearby capacitor pulling the line down.

Suggested Next Steps:​

• Check PV5G3S Power Rail: Trace the source of the missing 5V power rail (likely U7650).
• Check U8110 Circuitry: Inspect and probe around U8110 (responsible for PP0V95_S0_CPUVCCIO_REG_R), and check for potential shorts in the surrounding components.
• Diode Mode Testing: Continue performing diode mode checks on other critical power rails to ensure there are no further shorts or anomalies.
• Review Schematic for Power Sequence: Confirm the power-up sequence, as sometimes a missing rail early in the sequence will block the system from progressing to S0.