powers secondary standby components and USB subsystems. 3. Memory and PCH Rails ( +1.2V_PUPD / +1.0V_ALW ) Triggered after pressing the power button. +1.2V supplies power to the DDR4 RAM modules.
Integrated Platform Controller Hub (PCH) inside the CPU package. Super I/O / Embedded Controller (EC): ENE KB9022Q D.
The main DC-in power rail derived directly from the power adapter jack or the battery pack via the charging circuit.
If the +3.3V_ALW rail is present, but the board refuses to trigger or stuck looping, the firmware inside the SPI Flash ROM or the KB9022Q EC might be corrupted. Reflashing these chips with a verified bin file using an external programmer often resolves "no post" symptoms. Failed Entry MOSFETs La-e791p Rev 2.0 Schematic Diagram
Defines how power moves from the charger, through the DC jack, and into the charging IC (Charger IC) to create primary voltages ( 19V19 cap V 3.3V3.3 cap V
Provides exact specifications for resistors, capacitors, and IC part numbers needed for replacements. Key Components and Features of the LA-E791P
The La-e791p follows a but with HP-specific SIO enabling. powers secondary standby components and USB subsystems
: If a short circuit is found on a major rail like +B+ , limit a bench power supply to 1V and inject current while tracing the board with a thermal camera or isopropyl alcohol to locate the overheating component.
Technicians typically use this 59-page document for troubleshooting common motherboard issues: CSL50 LA-E791P Rev 2.0 Schematic | PDF - Scribd
The LA-E791P Rev 2.0 is an Intel-based platform with an AMD discrete GPU option. Key technical specifications include: The main DC-in power rail derived directly from
The La-e791p motherboard utilizes an advanced system architecture designed to balance power efficiency with performance. Understanding the layout of this board helps trace signals from the DC jack down to individual components.
Without the Rev 2.0 schematic, step 4’s voltage threshold (1.8V for enable vs 3.3V for logic) would be unknown—leading to misdiagnosis.
The 19V DC input enters through the DC-in cable and passes through a series of filtering capacitors, transient voltage suppression (TVS) diodes, and dual N-channel MOSFETs (often designated as PQ1 and PQ2 on Compal boards).