When troubleshooting an LA-C391P board using the schematic, follow this structural testing order to locate the fault.
Diagnosing a dead LA-C391P requires checking the power rails in a strict sequential order. The board translates the 20V DC input from the power adapter into several lower voltages. Main Input Rail ( +20V_ADADP / B+ )
The APW70 is a motherboard manufactured by Compal Electronics, primarily used in high-performance portable workstations and rugged devices. This specific board model is most commonly found in the HP ZBook 17 G3 Mobile Workstation . apw70 lac391p schematic portable
Because the APW70 and LAC391P form a flexible, high-efficiency power train, advanced hobbyists use the as a base for:
Features Anpec APW series PWM controllers (like the APW7142 or APW7070) for secondary voltage rails. 🔍 Key Component Identification When troubleshooting an LA-C391P board using the schematic,
The acts as the heavy lifter. While the APW70 handles logic and sequencing, the LAC391P drives external MOSFETs to generate the high-current main rails (often the 3.3V and 5V standby rails). It is a constant-on-time, synchronous buck controller.
Used to set the output voltage via a resistor divider. UGATE/LGATE: Gate drive signals for the external MOSFETs. EN (Enable): Logic high to turn on the regulator. 🛠️ Common Repair Scenarios No Power / No Charging: Main Input Rail ( +20V_ADADP / B+ )
The LA-C391P platform is designed around low-power, high-efficiency architecture to maximize portable battery life.
Tracing the schematic from the driver transistors to the output connector will reveal the current limiting resistors. These are common failure points if the output jack is shorted.
The power LED flashes briefly, then the system turns off instantly.