Blown DC-in MOSFET (PQ101) or shorted ceramic capacitor on +3.3V_ALW rail.
This comprehensive guide breaks down the architecture of the LA-C781P motherboard, maps out its core power rails, and provides actionable troubleshooting steps using the circuit diagram. 1. Document Overview and Specifications
: Often features the NPCE388N or similar multi-controller. Troubleshooting Common Power Issues La-c781p Schematic
Gate of PQ101 is driven by (BAT100). Schematic shows gate should be pulled low by charger IC’s ACDRV (pin 4). Measure ACDRV – 0V. BQ24780S is faulty.
You have a dead laptop. 19V is entering the board, but the fan doesn't spin. A generic multimeter check shows the 3.3V is present. Most people stop here and assume the BIOS is corrupt. Blown DC-in MOSFET (PQ101) or shorted ceramic capacitor
This is Compal's internal project code. The "LA" designates Compal, while the alphanumeric string represents the specific revision and platform.
Order replacement (common chip). After replacing, ACDRV rises to 25V, +PWR_SRC = 19.5V. Still no 3.3V_ALW. Document Overview and Specifications : Often features the
: Detailed repair discussions and partial boardviews can be found on DIY Laptop Repair Archive Channels : Some technicians share these files through Schematics|Boardviews Telegram Archives Telegram Messenger specific component value on this board, or are you trying to troubleshoot a particular symptom like a "no power" issue?
A schematic diagram is a visual representation of an electronic circuit, showcasing the relationships between various components, such as resistors, capacitors, and integrated circuits. These diagrams provide a simplified and concise way to illustrate complex electronic systems, making it easier for engineers, technicians, and enthusiasts to understand, design, and repair electronic circuits.
These sections cover the connections for the screen (LVDS or eDP), the keyboard, the touchpad, and the various external ports. If a specific port or peripheral isn't working, the schematic will show which pins and traces to test.
Modern Intel boards follow a strict power sequence. The LA-C781P schematic details this in a table (often on page 2 or 56).