Lac781p Schematic Top <LATEST>
Date: October 26, 2023 Subject: Identification and Schematic Retrieval for Component/Module LAC781P
The Compal LA-C781P (AHL51/ABL51) is a specialized AMD-based motherboard commonly found in HP 15-AF and HP 255 G4 series laptops. A schematic "top" overview typically focuses on the primary power distribution (VIN circuit) and the initial power-on sequence managed by the charging IC and Super IO. Core Circuitry & Power Rails
VIN Circuit (Input Power): The board starts with a 19V input from the DC jack.
Entry MOSFETs: Power passes through two N-channel MOSFETs (Check pins 1-3 for Source, pin 4 for Gate, and pins 5-8 for Drain).
Charging IC (BQ series): Often utilizes a BQ24725A (labeled BQ25A). Critical pins include: Pin 20 (VCC): Should read 19V.
Pin 6 (ACDET): Detection pin, typically between 2.4V and 3.1V.
Pin 16 (REGN): Linear regulator output, usually providing 6V.
Pin 4 (ACDRV): Gate drive for entry MOSFETs; must be higher than VIN (around 24V-25V) to allow power into the board. Initial Power Sequence (Standby)
RTC Section: The 3V RTC cell power is active even before the charger is connected.
3V LDO: One of the first rails to appear is the +3VLP (LDO), which powers the Super IO (EC) chip.
Always-On Rails: The +3VALW and +5VALW rails are generated to keep the board in a standby state, waiting for a power button trigger.
Power Button: Pressing the button should cause a voltage drop (typically 3.3V to 0V) on the specific trigger pin, signaling the Super IO to initiate the full power-up sequence. Troubleshooting "No Power" Symptoms
Short Circuit Check: Conduct a continuity test on the entry MOSFETs near the charging connector.
Super IO Diagnosis: If 3.3V is present at the power button but the board doesn't react (no current draw change), the Super IO may not be sending the "S5_ON" or "RSMRST#" signals to wake the chipset.
Coil Voltages: Verify voltages at various coils; for example, 0.9V is typical for RAM and 1.1V/1.05V for chipset/PCH logic.
For further technical data, you can find downloads for the LA-C781P Schematic or boardview on technical archives like ChinaFix or Telegram schematics channels.
LA-C781P Motherboard Schematic Overview Compal LA-C781P (often labeled as ) is a common motherboard found in series laptops. It features an AMD Stoney Ridge or similar APU architecture and utilizes the embedded controller. Technical Quick Specs : Compal ABL51 Common Laptop Models : HP 15-af011ur, HP 15-af series Embedded Controller (EC) : ENE KB9022Q Main PWM Controller : Often utilizes the for power rails (e.g., positive 3 cap V cap A cap L cap W cap P positive 5 cap V cap A cap L cap W cap P Troubleshooting Common Issues If you are dealing with a "No Power" (Dead) state, technicians frequently focus on the VIN circuit and the power sequence for the EC. Check the +3VALW rail : Ensure it is reaching pin 15 of the EC (KB9022Q). VIN Circuit
: Inspect the initial MOSFETs and the current sensing resistor for standard DC-in voltages. Resources for Repair Schematics & Boardview : You can find downloadable PDF schematics and boardview files on technical forums like DIY-LaptopRepair or specialized archives like Laptop-Schematics Community Guides : Detailed repair guides for specific models like the HP 15-af011ur are available on DIY-LaptopRepair
: Always verify all connections are secure and run diagnostics before and after board-level repairs. measurement or a for a particular component on this board?
(also known as the Compal ABL51 ) is a motherboard schematic frequently used in HP 15-af series lac781p schematic top
laptops. It is a common reference point for technicians troubleshooting "no power" or "no display" issues on these budget-friendly AMD-based machines. Board Specifications Model Name : Compal ABL51 LA-C781P. : Designed for AMD processors (e.g., A4-5000, A6-6310) using the BGA769 (FT3b) socket. : Supports (Low Voltage) RAM across two slots. Application : Primary motherboard for the notebook series. Troubleshooting "Top" Faults
If you are working with this schematic, these are the most reported issues encountered by repair experts: VIN Circuit Failure
: A common "dead" board symptom where the 19V main power rail enters the board but fails to distribute due to faulty MOSFETs or current sense resistors near the power jack. Missing Always-On Rails : Technicians often check for the
standby voltages. If these are missing, the laptop will not respond to the power button. BIOS/EC Corruption
: The board may appear dead or fail to trigger if the Embedded Controller (EC) or BIOS firmware is "frozen." A hard reset (pulling main and CMOS batteries) is a standard first step. Low Power Consumption
: A healthy standby board typically draws very low current (approx. 10mA). If it stays at this level after pressing the power button, it indicates a "no trigger" fault, often tied to missing power-on signals from the Super I/O chip.
The is a motherboard manufactured by Compal, primarily used in the HP 15-AF011UR, HP 15-AF series, and HP 255 G4 laptops. While it is a Compal design, it is frequently misassociated with Lenovo models in general schematic databases due to the shared "LA-" naming convention. Core Component Overview Based on typical
configurations, here are the primary components found on the top side of the board: Processor (APU): Integrates the CPU and GPU (e.g., AMD A6-6310 Go to product viewer dialog for this item. Charging Controller: Uses the Go to product viewer dialog for this item.
(labeled as BQ25A) IC to manage battery charging and input voltage protection. Embedded Controller (EC): Typically a
or similar, managing power-on signals and keyboard interface.
Power Rails: Features dedicated coils for +3VALW and +5VALW "always-on" voltages. Critical Troubleshooting Sections
When using the schematic to diagnose "No Power" issues, focus on these top-layer sections: VIN / First MOSFET Section: Check for 19V at the drain of the first N-channel MOSFET.
Common Fault: If the gate voltage is missing, the BQ25A (pin 4, ACDRV) may not be outputting the required ~25V boost to open the MOSFET. Step-Down (+3V/+5V) Section: Verify +3VALW at the RTC cell and battery connectors.
Check +3VLP_EC (LDO voltage) which is required for the EC chip to wake up the system. Power-On Sequence: ACIN: The EC must detect the charger signal. EC Wakeup: 3.3V LDO must be present.
RSMRST#: Signal sent from EC to the chipset/APU to release it from reset.
S3/S5 Signals: The APU returns SLP_S3 and SLP_S4 signals to enable the RAM and CPU core voltages. Where to Find the Schematic
You can access technical drawings and component placement diagrams from these sources:
In the dimly lit corner of "The Silicon Graveyard," a small repair shop tucked away in a bustling tech district, stared through his microscope. Before him lay the
, the motherboard of an HP 15 series laptop that had arrived "D.O.A."—Dead on Arrival. For hours, Elias had been chasing ghosts. He had the LA-C781P schematic Date: October 26, 2023 Subject: Identification and Schematic
open on a second monitor, its "Top" page displaying the complex power rail architecture like a city map drawn in neon lines. He knew the 19V main rail was entering the board, but somewhere between the DC-in jack and the CPU, the lifeblood of the machine was vanishing.
"Come on, talk to me," Elias whispered. He traced the schematic’s path to the VIN circuit. According to the diagram, a pair of MOSFETs near the charging port should have been passing voltage, but they were as cold as ice. He checked the gate voltage—zero. The tiny PWM controller that was supposed to wake them up was silent.
The "Top" view of the schematic wasn't just a technical drawing; it was a puzzle. He looked at the component designations: PQ301, PR302. On the physical board, they were smaller than grains of rice. He found a microscopic speck of corrosion near a capacitor—hardly visible to the naked eye, but on the high-resolution boardview, it was a bridge to nowhere.
With a steady hand, Elias applied a drop of flux and touched his soldering iron to the board. A tiny puff of smoke rose as he replaced the faulty component. He held his breath, reconnected the power supply, and watched the ammeter. 0.010 amps... 0.150... then a jump to 0.450.
The fan gave a sudden, sharp spin. On the bench, the HP logo flickered to life. The
had been resurrected, not by magic, but by following the map hidden in the schematic. Elias leaned back, the blue glow of the "Top" schematic page reflecting in his tired eyes—another ghost laid to rest. about this specific motherboard or a different style
The Compal LA-C781P (also known as the ABL51) is a motherboard found in various HP 15-AF and HP 255 G4 series laptops. Understanding its schematic and top-level layout is essential for technicians diagnosing "no power" states or hardware failures in these budget-friendly AMD-based machines. Motherboard Overview and Specifications
This board is designed around an AMD platform, typically featuring soldered AMD A6-6310 or AMD E2-series APUs (Accelerated Processing Units). Because the CPU and GPU are often integrated into a single chip, the layout is more streamlined than older discrete-component boards.
Model Identification: Look for "LA-C781P" or "ABL51" printed directly on the PCB, usually near the RAM slots. Platform: AMD Carrizo-L or Beema architecture.
Memory: Typically supports DDR3L (Low Voltage) RAM across two slots.
System Controller: Uses the KB9022Q Embedded Controller (EC/Super I/O), which manages power sequencing and keyboard input. Top-Side Component Layout
The "top" of the schematic refers to the primary component side. Key landmarks on the LA-C781P top layout include:
Charging Section (VIN Circuit): Located near the DC-in jack, this area features the bq24725A (often marked as BQ25A) charging IC. It manages the initial 19V rail (B+) and controls the N-channel MOSFETs that gate power to the rest of the system.
Step-Down Converters (3.3V/5V): Look for the RT8243 (or similar) PWM controller. This chip generates the "always-on" (ALW) voltages required to power the EC and BIOS before the user even presses the power button.
APU/SoC Centerpiece: The large BGA chip in the center is the AMD APU. Around it, you will find the VCORE power phases, consisting of high-current inductors (coils) and MOSFET pairs.
Peripheral Interfaces: The top side also hosts the BIOS SPI chip, WLAN slot, and various headers for the screen (LVDS/eDP), keyboard, and touchpad. Troubleshooting with the Schematic
When the LA-C781P fails to power on, technicians focus on specific "power rails" defined in the schematic:
B+ (19V): If this is missing at the main current-sensing resistor (CLR), the issue is likely in the entry MOSFETs or the BQ25A charging IC.
+3VALW / +5VALW: These must be present for the laptop to respond to the power button. A short in the KB9022Q EC is a common cause for the +3.3V rail being missing. Let’s walk through a real-world build based on
EC_ON / Power Sequencing: The schematic tracks the signal from the power button to the EC, which then triggers the S3 and S0 power states. Where to Find Schematics and Parts
Official schematics for the LA-C781P are often found on technical forums and archives:
Schematics & Boardviews: Communities like the VLab Technical Forum or Notebook1 often share these files for repair purposes.
Replacement Boards: If the PCB is beyond repair, you can find replacement ABL51 LA-C781P motherboards on marketplaces like Amazon or StoneTaskin.
Are you currently troubleshooting a no-power issue or looking for a specific component location on this board?
Let’s walk through a real-world build based on the schematic top.
When implementing the lac781p schematic top on a PCB, the pin assignment is non-negotiable:
Many beginners confuse this with the TO-220 packaging of other regulators. Always verify the heat sink tab: on the LAC781P, the tab is typically connected to Pin 2 (Ground), which simplifies mounting to a conductive heatsink.
Here is how to construct a standard application circuit based on the lac781p schematic top:
Two critical features appear in the top schematic:
The keyword "lac781p schematic top" encompasses more than just a diagram—it represents the complete understanding of a reliable, classic linear regulator from its high-level circuit connections down to the physical placement on a PCB’s top layer.
By mastering the standard application circuit (input filtering, regulator, output decoupling) and recognizing that LAC781P is functionally a 7812 in TO-220 package, you can confidently repair old equipment, design new power supplies, or adapt it into larger audio or embedded projects.
Remember these key takeaways:
Whether you are a student building your first bench supply or a technician restoring legacy hardware, the LAC781P’s straightforward top-level schematic will serve you reliably for years to come. Keep a copy of this guide handy, and you’ll never be lost when you encounter that enigmatic three-terminal regulator labeled LAC781P.
Appendix: Quick Reference – LAC781P Pinout (Top View)
LAC781P (TO-220)
____________________
| (Tab connected to Pin 2 - GND)
| | | |
| 1 2 3
|__|__|__|
| | |
VIN GND VOUT
For further reading, search for "L7812CV datasheet" and "linear power supply design tutorial."
If you're referring to a specific electronic component, a chip, or a part of a larger system, here are a few potential areas where you might find relevant information:
Given the specificity of your request and the lack of general information on "LAC781P Schematic Top", here is a general template for what a write-up on a schematic or a component might look like:
The input pin receives unregulated DC voltage (typically 2-3V above the output voltage). Internally, the input first passes through a start-up biasing network. This section powers the internal reference and provides base current to the pass transistor during initial power-on.