Ensure CPU Vcore is present. If missing, check the PWM controller signals shown in the schematic.
While schematics are PDF documents, the verified schematic often maps directly to the boardview file, allowing you to see the physical layout. Core Components and Power Rails of the LA-E791P
Use an oscilloscope to check for data activity on Pin 1 (CS#), Pin 2 (DO), and Pin 5 (DI) of the BIOS chip right after powering on the board. If there is no communication, desolder the flash IC and reprogram it using a verified dump with a clean Management Engine (ME) region.
When dealing with common issues like no-power states, liquid damage, or short circuits on the main power rail, a verified schematic allows you to trace signals, verify power rail voltages, and identify failed surface-mount devices (SMDs). Motherboard Architecture Overview lae791p rev 20 schematic diagram verified
Ceramic filtering capacitors (MLCCs) decoupling the 19V rail near the CPU or GPU phases frequently crack and short to ground.
The EC releases the sleep signals ( S5_ENABLE , SUSP# ), turning on the memory rails (+1.2V) and secondary run rails. Finally, the CPU PWM IC turns on and +VCC_GT . 3. Common Failure Points on the LA-E791P Motherboard
Power enters the board via the DC-IN jack and immediately passes through a protection circuit. The raw 19V input from the charger. Ensure CPU Vcore is present
Once the B+ rail is stable, it powers the Always-On (ALW) power management integrated circuit (PWM IC), usually an (+3.3V) and SY8288CRAC (+5V) setup or a combined controller.
The Compal LA-E791P motherboard is commonly found in mainstream Dell Inspiron and Vostro series laptops (such as the Dell Inspiron 15 3567 / 5567 series) powered by Intel 7th Generation Core processors (Kaby Lake U-architecture) or 6th Generation (Skylake) processors. Key Specifications:
Check the current sensing resistor directly after the second input MOSFET. If you do not measure 19V here, the gate voltage from the charging IC is missing, or a downstream short circuit is pulling the rail to ground. 2. The 3.3V and 5V Always-On Rails Core Components and Power Rails of the LA-E791P
| Area | What to Look For | Typical Fix | |------|------------------|-------------| | | All IC VCC pins connect to a single, appropriately named net ( +5V , VDD , AVDD ). Decoupling caps placed close to each pin. | Add missing bulk capacitor (e.g., 10 µF electrolytic) near regulator output. | | Ground Plane | All ground pins converge onto a single GND net (or split‑ground if intentional). | Merge AGND and DGND if not required to be separate, or clearly label split‑ground zones. | | Signal Routing | No floating inputs, no unconnected outputs. All UART, SPI, I²C, etc., have proper pull‑ups/pull‑downs. | Add 10 kΩ pull‑up to I²C_SCL if missing. | | Clock Trees | Clock sources ( OSC_IN , CLK_OUT ) have proper termination, load caps, and are not shorted to other nets. | Verify crystal load caps match crystal spec (e.g., 22 pF each). | | Test Points | Critical nodes (e.g., VREF , VBAT , RESET , high‑speed signals) have dedicated test points. | Insert TP1 at RESET_N . | | Unused Pins | Unused pins are either tied to a defined level (GND/VCC) or left open with a “No Connect” (NC) annotation. | Tie floating NC pins to ground through a 1 MΩ resistor if they are high‑impedance inputs. |
The LA-E791P is a high-density motherboard typically featuring: Integrated Intel Core i3/i5/i7 (6th or 7th Gen). Memory: DDR4 RAM slots.
The schematic diagram, often found as the "lae791p rev 20" variant, is a vital document for anyone repairing or analyzing an Acer laptop. It provides an essential roadmap to the motherboard's inner workings and is a prerequisite for professional chip-level repair. By using a verified schematic from a trusted source and understanding how to interpret its information, complex electronics diagnostics become a manageable and highly successful endeavor.
Dual-channel DDR4 SODIMM slots (supporting up to 32GB).
Identify the expected voltage at every point, from main power ( +19Vpositive 19 cap V ) to CPU VCC (