La-e791p Rev 2.0 - Schematic Diagram

Mastering the LA-E791P Rev 2.0 Schematic Diagram: The Ultimate Repair Guide for Vostro 5471 & Inspiron 5471

Guide: LA-E791P Rev 2.0 Schematic Diagram

4. Common Failures & Schematic-Based Fixes (No boardview needed)

Failure C: No Display / GPU Error Code 43

Symptom: Laptop boots to Windows but reboots when installing NVIDIA drivers, or stays black on external monitor. The Fix: The GPU core voltage may be unstable or the BIOS configuration lost.

• Schematic Use: Locate the NVVDD (GPU Core) power supply. Check the feedback resistor divider (e.g., R672 and R677). A single corroded resistor here blows the voltage out of spec. The schematic gives you the math: Vout = 0.6V * (1 + R_top/R_bottom).

1. The Adapter Input & Charging Circuit (Page 1-3)

Look for the BQ24780S (IC U5000). This is the primary gatekeeper. The schematic reveals the pinout: La-e791p Rev 2.0 Schematic Diagram

• Pin 5 (ACDET): Adapter detect threshold (2.4V – 3.15V).
• Pin 4 (ACOK): Open-drain output (Should be 3.3V when adapter is good).
• Pin 28 (REGEN): Main power gate driver.

Common fault: If ACDET is below 2.4V, the board will not turn on. Check voltage divider resistors (R5001/R5002) listed in the schematic. Mastering the LA-E791P Rev 2

Page 40-45: Embedded Controller (EC)

The EC is the "brain" for turning on power. The schematic reveals the logic levels: LID_SW#, AC_IN#. A common failure is the EC losing its program (corrupt BIOS). The diagram tells you which SPI pins (CS#, SO, SI, CLK) to probe to see if the EC is talking to the main BIOS. Schematic Use: Locate the NVVDD (GPU Core) power supply