Top: Lac781p Schematic

The LA-C781P (also known as ABL51) is a motherboard manufactured by Compal for the HP 15-AF series laptops.

Steps:

  1. Draw the schematic top on paper as shown in Part 3.
  2. Layout on perfboard following the top-layer component positions.
  3. Solder starting from the transformer secondary to the bridge, then C1, then LAC781P, then output caps.
  4. Test without load – measure Vin (~16V DC), then Vout (12V ±5%).
  5. Add load – a 12Ω resistor (1A) will test regulation.
  • Testing checklist

    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 LAC781P. lac781p schematic top