Test the inductors for +3VALW and +5VALW . If +3VALW is missing, check if the EC chip is hot, which indicates an internal short. Symptom 2: Power LED Blinks, No Boot (No Post)
Right next to the SoC, the top layer features , arranged horizontally or staggered to maximize signal integrity on the multi-layer PCB. 2. DC-In and Primary Power Generation Stage
The LAD402P motherboard is built around an Intel SkyLake or Kaby Lake U-processor (Core i3/i5/i7 or Celeron/Pentium SoC). Because it is a System-on-Chip (SoC) architecture, the traditional Northbridge and Southbridge are integrated directly into a single package. Key Integrated Interfaces:
When engineers refer to the of the LAD402P, they mean two things:
: Components are labeled with letters (e.g., PU for Integrated Circuits, PL for Inductors/Coils, PC for Capacitors, PR for Resistors). lad402p schematic top
Features integrated Intel Core i5/i7 U-series processors (e.g., i5-7200U), balancing battery efficiency with performance.
If you identify a promising candidate like or PTC402P , the next step is to download its official datasheet. This document will contain the pinout, electrical specifications, typical application circuits, and mechanical dimensions, allowing you to compare it with your physical component and confirm a match.
The top layer ("Top Side") of the LAD402P houses the high-density surface-mount technologies (SMT) that require the most thermal management and physical accessibility. This includes:
: Centrally located, often surrounded by large inductors (coils) and MOSFETs that form the CPU Core Power (+CPU_CORE) . Test the inductors for +3VALW and +5VALW
To fully execute repairs using the LA-D402P schematic, a diagnostic bench should ideally be equipped with specialized hardware:
[DC Jack / Battery Input (+PWRSRC)] │ ▼ [+3VALW / +5VALW Standby Rails] │ ▼ [System PMIC / Embedded Controller] │ ▼ [+1.8V / +1.05V PCH Core Rails] │ ▼ [Memory VCC Rails] │ ▼ [CPU VCCIN / Core Voltage (S0)]
While the full PDF schematic is a proprietary technical document, you can find the specific layout and pinout details through these resources: Top-Side Layout:
: Because the physical ports are anchored directly to this board layout, regular cable plugging can strain solder joints. Additionally, liquid entering the USB ports instantly shorts out the adjacent 20V line to data pins, burning out the PD controller chip. Key Integrated Interfaces: When engineers refer to the
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Set multimeter to resistance mode. Test the large system inductors (3.3V, 5V, CPU core, and RAM rails) relative to system ground. Low ohms indicates a shorted capacitor or IC on that rail. Verify the +19V main line passes the safety MOSFETs.
Be cautious when soldering near the CPU or GPU areas on the top layer. These areas feature thick inner copper ground planes that act as heat sinks, requiring a high-wattage soldering iron or preheater to prevent pad lifting.
: Commonly managed by Texas Instruments (TPS series) or Cypress PD controllers, which negotiate voltages up to 20V.
+---------------------------------------------------+ | | | [13] [14] [23] [24] | | | (NO-1) (NO-2) | | | [21] [22] [31] [32] | | (NC-1) (NC-2) | | | | (Actuator plunger entrance - bottom side) | +---------------------------------------------------+