Look for "LA-C781P" or "ABL51" printed directly on the PCB, usually near the RAM slots. Platform: AMD Carrizo-L or Beema architecture.
Before the power button is even pressed, the LAC781P generates "Always" voltages. Powers the Super I/O (KBC) and the BIOS chip. +5VALW: Powers secondary peripherals and USB standby ports.
: Step-down buck inductors for +3VALW and +5VALW . Normal readings should yield high impedance to ground. Low ohms here indicate a dead consumer chip on that respective power rail. lac781p schematic top
If the source of the entry Mosfets has 0V, check if the bq25A charging IC is outputting ~25V on Pin 4 ( ACDRV ). If it is 0V, the IC may be faulty or sensing a short circuit.
Indicates PCIe lane allocations (e.g., x2, x4) and data bus types. Look for "LA-C781P" or "ABL51" printed directly on
Whether you are a student building your first bench supply or a technician restoring legacy hardware, the LAC781P’s straightforward top-level schematic will serve you reliably for years to come. Keep a copy of this guide handy, and you’ll never be lost when you encounter that enigmatic three-terminal regulator labeled .
: The battery charging inductor. Check for battery charging voltage oscillation here when a battery is installed. Powers the Super I/O (KBC) and the BIOS chip
Consult the schematic to find the PWM controller for the CPU.
Technicians often use the LA-C781P schematic to solve common power-related failures:
Signals ending in "#" (e.g., PLT_RST#) are "Active Low," meaning they are functional when at 0V.
Understand the power-on sequence (S5, S4, S3, and S0 states).
Rajkumar SM is the founder of SoftwareTestingMaterial. He is a certified Software Test Engineer by profession and a blogger and YouTuber by choice. He has extensive experience in the field of Software Testing. Furthermore, he loves spending time with his wife and their cute little kid, 'Freedom.'
