La-c781p: Schematic

Page 48: +3.3V_ALW comes from TPS51285 (PU501). Measure:

Lesson learned: Without the schematic, you’d never trace the EN signal back to a self-starting regulator.

Modern Intel boards follow a strict power sequence. The LA-C781P schematic details this in a table (often on page 2 or 56).

Simplified sequence:

If any step fails, the schematic helps you identify which signal is missing.

No. LA-C761P is for Dell Precision 5510/5520 (different form factor, different GPU power delivery). Always verify the exact number on the board.

This blog post is designed for a technical audience interested in laptop repair and electronics. It focuses on the Compal LA-C781P motherboard, commonly found in the HP 15-af series

Mastering the HP 15-af Repair: A Guide to the LA-C781P Motherboard

Repairing modern laptops often feels like navigating a maze without a map. If you are working on an HP 15-af series laptop, that map is the Compal LA-C781P

schematic. Whether you are dealing with a "no power" issue or a liquid spill, understanding this specific board layout is the key to a successful repair. 1. Identifying the Board

(also known as ABL51) is a common motherboard revision for the HP 15-af line, typically powered by AMD Beema/Mullins processors

. Before diving in, always verify the silk-screened model number near the RAM slots to ensure you have the correct documentation. 2. Common Failure Points Based on technician reports from communities like DIY-LaptopRepair , here are the most frequent issues: DC Jack Failures:

The power connector is prone to loosening, which can lead to arcing and "smoke from the socket". Corrosion near the KBC/EC:

The Multi-Controller (often an ENE chip) is a frequent victim of liquid damage. Charging Circuit Issues:

If the laptop won't charge, the schematic is essential for tracing the rail through the first and second MOSFETs. 3. Essential Power Rails to Check

When using the schematic for a dead board, follow this startup sequence: Main power rail from the adapter. +3VALW / +5VALW: Always-on rails required for the power button to function. Power supply for the keyboard controller. 4. Pro-Tips for the Bench Use a Boardview: While the schematic tells you components are connected, a Boardview file tells you

they are physically located. This is vital for finding tiny resistors and caps on the LA-C781P. Safety First:

Always run diagnostics before and after a board-level repair to ensure no other components (like the HDD or screen) were affected. Stay Organized:

Use magnetic mats or labeled containers to keep track of the different screw sizes found in the HP 15-af chassis. Conclusion

The LA-C781P might be a budget-friendly board, but its repair requires precision. Armed with the schematic and a decent multimeter, most power-related failures are solvable. Are you stuck on a specific voltage rail for this board? Tell me the component number

(e.g., PL9 or PQ302) you're troubleshooting, and I can help you trace the circuit.

The LA-C781P (Revision 1.0) is a motherboard schematic specifically for the HP 15-AF series notebooks, often paired with the ABL51 motherboard designation. This schematic is a vital resource for technicians diagnosing "dead" units or power-on failures. Technical Overview Platform: AMD Beema/Mullins APU platform. Key Components: CPU: Integrated AMD APU. RAM: Typically supports DDR3L memory modules.

KBC/EC: Embedded Controller (often ENE or similar) managing power sequencing.

Power Circuit: Features a complex VIN circuit and 3V/5V LDO regulators. Common Repair Scenarios

The LA-C781P is frequently associated with the following motherboard issues:

No Power (Dead Motherboard): Often traced back to the VIN circuit or a failure in the 19V rail distribution.

LDO 3.3V Short: A common point of failure where the KBC (keyboard controller) shorts out, preventing the charging light from illuminating. La-c781p Schematic

High Fan Speed / No Display: Can occur after replacing the KBC if the firmware is not correctly flashed or if there are issues with the AMD APU's power rails. Where to Find Schematics and Boardviews

You can access the LA-C781P schematic and boardview through professional repair repositories:

Laptop-Schematics: Offers specific files for Compal/OEM models like the J781P and similar variants.

LaptopSchematic.com: A massive library featuring over 72,000 files for major brands.

Telegram Archive: A popular community resource for free PDF schematic and boardview downloads (BRD/BDV formats). Pro Tips for Troubleshooting schematics|boardviews| ARCHIVE – Telegram

The LA-C781P (also known as the ABL51) is a laptop motherboard manufactured by Compal Electronics, primarily used in the HP 15-AF series and the HP 255 G4. Finding the schematic is essential for board-level repairs, such as troubleshooting "no power" issues or identifying failed components like the charging IC or MOSFETs. Core Specifications Platform: AMD Beema / Mullins

Processors: Integrated AMD APUs (e.g., A6-5200, A6-6310, A8-7410) Memory: DDR3L RAM (usually 2 slots, supporting up to 16GB)

Graphics: Integrated AMD Radeon or Discrete R5 M330 (depending on sub-model)

Power Management: Often utilizes the BQ24725A (marked BQ25A) charging IC for voltage regulation. Troubleshooting High-Traffic Areas

Based on common repair data for this board, technicians often focus on these specific schematic sections: VIN / Charging Section:

The first and second input MOSFETs (N-channel) often fail to open if the charging IC doesn't generate the required "ACDRV" gate voltage (~25V). Check for 19V at the drain of the first MOSFET. 3.3V / 5V Always-On Rails: If these are missing, the power button will not respond.

The schematic identifies the specific "Step-Down" controller responsible for these rails. BIOS / EC:

Corruption in the 4MB SPI Flash chip is a common cause of "Dead" or "No Display" symptoms.

The EC (Embedded Controller) manages the power-on sequence and keyboard functions. Where to Find the Schematic

While the full PDF is proprietary, it is widely archived on technical forums and specialty repositories:

Technical Archives: Professional repair sites like Laptop-Schematics and ChinaFix often host verified versions.

Community Forums: You can often find repair guides or partial schematic snippets on DIY-LaptopRepair.

Boardview Files: Many sources provide a .BDV or .TVW file alongside the schematic, which allows you to visually locate components on the physical board.

Are you troubleshooting a specific symptom (e.g., no power, water damage, no display) on an LA-C781P board right now? I can help you identify which pins or components to measure if you describe the behavior.

The Compal LA-C781P (ABL51) motherboard is commonly found in laptop models like the HP 15-af011ur. This board is designed for AMD-based systems, specifically utilizing the AMD Stoney Ridge or similar APU architectures. Core Components & Specifications

The following components are central to the LA-C781P architecture:

Processor (APU): Integrated AMD processor (e.g., AMD A8-7410). Memory: Typically supports DDR4 RAM.

Power Management (IC): Uses the bq24725a (marked bq25a) charging IC for power regulation and battery management.

Embedded Controller (EC): Often features the NPCE388N or similar multi-controller. Troubleshooting Common Power Issues

Repair technicians often encounter "No Power" or "No Start" conditions with this board. Common diagnostic steps include:

Initial Voltage Check: Verify 19V input at the DC jack. In many failure cases, 19V is present at the first N-channel MOSFET drain but fails to pass through to the source because of a missing gate signal from the charging IC. Charging IC (bq25a) Pins: Pin 20 (VCC): Should have ~19V. Page 48: +3

Pin 6 (ACDET): Should have ~2.4V to 2.8V to detect the adapter.

Pin 4 (ACDRV): Should ideally be ~25V to turn on the input MOSFETs. If this is 0V, the IC may be faulty or sensing a short circuit downstream.

LDO Voltages: Check for +3VALW and +5VALW. The 3.3V LDO should be available at the RTC battery and power button connectors even if the main power rails are off. Reference Resources

For detailed diagrams and step-by-step guides, refer to these specialized platforms:

Schematic Repositories: Search for "LA-C781P" on sites like Laptop-Schematics.com or VLab.su for professional-grade boardview and PDF files.

Repair Walkthroughs: Video guides on channels like OM Chip Level Solution provide visual steps for solving "No Power" issues on this specific board.

Alternative Schematics: The LA-C701P is often cited as a similar Broadwell-based architectural reference, though not identical.

Are you experiencing a specific fault, such as the board not powering on or failing to charge the battery?

Compal LA-C781P (ABL51) is a motherboard schematic and boardview commonly used for repairing

notebook series laptops. These laptops typically feature AMD processors like the Repair Community Insights Common Failure Points

: Technicians often use this schematic to troubleshoot "no power" issues where 19V enters the board but consumption remains stuck at low levels (e.g., ~10mA), indicating a failure in the power-up sequence or power rails. Key Components : The board integrates the (often BGA/soldered), the

or similar EC/KBC chip, and supports DDR3L or DDR4 memory depending on the specific revision. Compatibility Note

: While most LA-C781P boards are for HP AMD systems, some listings for similar model numbers (like LA-K491P) refer to Dell Latitude 5420 models, so verify your exact board silk-screen before downloading files. Where to Find Schematics & Parts

If you are performing component-level repair, you can find the schematic and boardview on specialized technician platforms: Schematic Repositories : Sites like NotebookSchematics.com Laptop-Schematics.com

offer downloadable PDF diagrams and BoardView (.CAD or .BRD) files. Replacement Boards

: If the board is beyond repair (e.g., a shorted CPU), replacement LA-C781P motherboards are available through retailers like StoneTaskin or marketplaces like AliExpress Local Suppliers : In regions like India, vendors such as Caviar Technologies

on IndiaMART stock these boards for approximately ₹3,000 to ₹3,500. full PDF schematic

to fix a specific power rail issue, or are you trying to find a replacement motherboard for your laptop?

hp pavilion 15 ac/15-af amd laptop motherboard la-c781p - IndiaMART

Compal LA-C781P (ABL51) is a laptop motherboard commonly found in the

series notebooks powered by AMD processors. Understanding its schematic is essential for diagnosing "No Power" or "No Display" issues. 1. Board Overview Manufacturer: Model Code: ABL51 LA-C781P Processor (APU):

Typically features AMD Beema/Mullins processors (e.g., AMD A6-7310 or A8-7410) soldered to the board. Super I/O (EC):

, which handles power-on sequencing, keyboard input, and battery management. 2. Primary Power Rails A typical repair starts by verifying these rails in order:

The main power rail (VIN). It enters through the DC jack and passes through two entry MOSFETs controlled by the charging IC. +3VALW / +5VALW: "Always-on" rails. On this board, the RT8243 (PU2) often acts as the PWM controller for these voltages.

A low-dropout voltage generated by the standby IC, required for the EC (KB9022Q) to begin the power-up sequence. 3. Common Faults & Troubleshooting No Power / Dead:

(Charging IC). Pin 20 should have 19V, and Pin 6 (ACDET) should be around 2.4V to 3.1V to enable the entry MOSFETs. No 3.3V/5V Standby: Lesson learned: Without the schematic, you’d never trace

If the LDO is missing, the Super I/O will not trigger the power button signal. Technicians often find short circuits on the +3VALW rail caused by a failed EC or a ceramic capacitor. Fan Spinning High Speed:

Often occurs after a BIOS flash or EC replacement if the firmware version (BID) does not match the hardware precisely. 4. Component Reference Table Common Part Number 3V/5V Standby Controller Super I/O / EC ENE KB9022Q Charging Controller BQ24725A (Marked BQ25A) SPI Flash Memory Typically 8MB (e.g., Winbond 25Q64)

Comprehensive Guide to the Compal LA-C781P Schematic The LA-C781P (also known as the AAL10) is a widely used motherboard manufactured by Compal, found primarily in the Dell Latitude 3460 and 3560 series. For laptop repair technicians and electronics enthusiasts, having the schematic is the difference between a guessing game and a precision repair.

This guide explores the architecture of the LA-C781P, common failure points, and how to use the schematic to revive a "dead" board. 1. Board Overview and Specifications

The LA-C781P is designed for 5th and 6th Generation Intel Core processors (Broadwell/Skylake U-series). Key features typically found on this board include: Platform: Intel Broadwell/Skylake-U (integrated PCH).

Memory: Dual-channel DDR3L or DDR4 (depending on the specific revision).

Graphics: Integrated Intel HD Graphics (or optional discrete NVIDIA GPU on some variants). Controller: ENE KB9022Q embedded controller (EC). 2. Why the Schematic is Essential

When a Dell Latitude 3460 won’t power on, the schematic serves as your map. It provides:

Power Rails: Information on the +3VALW, +5VALW, and +1.0V_Core rails.

Component Values: Precise resistance and capacitance for SMD components that may be charred or missing.

Pinouts: Connections for the BIOS chip, EC, and charging IC (usually an ISL series).

Signal Paths: Tracking the PS_ID signal from the Dell charger to the EC. 3. Common Failure Points on the LA-C781P

Based on technician feedback, the LA-C781P often suffers from a few specific issues: A. The "PS_ID" Circuit

Dell laptops require a signal from the center pin of the charger to identify the wattage. If the MOSFET or resistor in this circuit (found in the first few pages of the schematic) fails, the laptop may run but won't charge the battery. B. Shorted Input MOSFETs

The entry point of the 19V DC-in often features two N-channel MOSFETs. If these are shorted, the board will be completely dead with no lights. The schematic helps identify the "gate" signals coming from the charging IC to see if they are being driven correctly. C. Corrupted BIOS/EC Firmware

The ENE KB9022Q is a programmable chip. If the board has power but won't "post," the schematic helps you locate the SPI header or the pins needed to reflash the EC firmware. 4. Navigating the Schematic

When you open the LA-C781P PDF, focus on these critical pages:

Block Diagram: Usually Page 2. Gives a bird's-eye view of how the CPU connects to the RAM, SSD, and Screen.

Power Sequence: This chart tells you the order in which voltages must turn on. If +3VALW is missing, +5VALW will never start.

Voltage Regulators: Dedicated pages for the 3.3V/5V "Always-On" buck converters. 5. Troubleshooting Steps

Visual Inspection: Look for liquid damage or burnt components.

Check Main Rail (B+): Ensure 19V is present after the entry MOSFETs.

Check Standby Power: Verify 3.3V on the power button and the BIOS chip (Pin 8).

Signal Tracing: If the power button is pressed but nothing happens, use the schematic to trace the PWR_SW# signal to the EC. Conclusion

The Compal LA-C781P is a robust board, but like all hardware, it is prone to wear and electrical faults. Utilizing the schematic allows you to perform "board-level" repairs rather than expensive whole-board replacements. Whether you are dealing with a "No Power" or "No Charging" scenario, the schematic is your most powerful tool.