Check for a short circuit to ground on the +3VALW and +5VALW coils. Power On, No Display (Spinning Fan) Measure voltage on the RAM coil and CPU VCORE coils.
Locating the specific is important because subtle differences in motherboard revisions can lead to incorrect component replacement. A dedicated Rev 1.0 PDF ensures you are analyzing the correct voltage rails and component pinouts for your HP Notebook 15-ac. 2. Key Technical Specifications & Components Platform: Compal LA-C921P (ASL50) Revision: 1.0 Compatible Laptops: HP 15-ac series, 15-af, HP 250/256 G4. CPU: Intel Skylake U-Series (soldered/BGA). Chipset: Integrated (SOC). RAM: DDR3L SDRAM (Single Slot). Video: Discrete AMD Radeon or Intel Integrated. 3. Top Repair Cases & Diagnostic Paths
Help troubleshoot a if you provide more symptoms. What are you currently trying to fix on this board? Share public link
Fan spins at maximum speed with no display, loops continuously, or turns on for 3 seconds and shuts off.
A short-circuit on the primary 19V +VIN rail, frequently caused by shorted ceramic multi-layer capacitors (MLCCs) near power rails like PL5 , PL6 , or PL7 . asl50 lac921p rev 10 schematic exclusive
The ASL50 LA-C921P is designed around a highly integrated System-on-Chip (SoC) architecture, typical of modern mid-range laptops focused on energy efficiency and cost-effectiveness.
Before the user presses the power button, the motherboard must generate low-voltage rails to power the Embedded Controller (EC) and the power button circuit itself.
We invite you to share your thoughts and feedback on this exclusive schematic. What do you think of the design? How do you plan to use it? Let us know in the comments section below.
Find the main current-sensing resistor (usually labeled PR301 or similar near the charging area). If you have 19V here, your main power distribution path is intact. Check for a short circuit to ground on
Video tutorials on YouTube provide step-by-step motherboard checking processes specifically for the LA-C921P. ASL50 LA-C921P REV 1.0 SCHEMATIC HP Notebook 15-ac
: The CPU power rails. If these are missing, the CPU will not initialize. +1.8VRUNpositive 1.8 cap V sub cap R cap U cap N +1.05VRUNpositive 1.05 cap V sub cap R cap U cap N : Power to memory and PCH components. Common Faults and Schematic Solutions
Having the schematic allows a technician to diagnose the most frequent failures reported on this motherboard. Below are the common problem areas, along with the components involved.
| | Likely Area | Key Components (as per schematic) | |-------------|----------------|-----------------------------------------| | Laptop does not power on, no LED | Charger input circuit | PQ202 , PQ203 (input MOSFETs), PU201 (charger IC, often BQ735) | | Fan spins, but no display | BIOS corruption or EC failure | BIOS chip ( 25Q64FVSIQ ), EC ( ENE KB9022Q ) | | Laptop only works on battery, not on AC adapter | Charger detection and ACOK signal | ACDET , ACOK on charger IC, and the ADP_ID line going to the EC | | Short circuit on power rail | Failed capacitor or MOSFET on a voltage rail | PL9 inductor (3.3V rail), PL15 inductor (GPU core rail) | | Embedded controller (KBC) not reading | Wiring mismatch between programmer and board | KSO3 , KSI4 , KSI5 , KSI6 , KSI7 pins of the EC | | No 3V/5V standby voltages | Main power management IC | PU6 (SY8032ABC regulator) and associated resistors like PR92 | A dedicated Rev 1
Technicians tracking issues on the ASL50 LAC921P often encounter a few recurring symptoms. No Power / Dead Motherboard Check the main current sensing resistor for 19V.
Reviews from repair communities highlight the following utility for this schematic: Power Sequencing
Integrates an Intel Core i3/i5/i7 Processor (Broadwell-U or Haswell-U platform) directly soldered to the board. The CPU, Graphics (Intel HD Graphics), and Platform Controller Hub (PCH) reside on the same silicon die.
Always-on power rail. Powers USB ports and auxiliary internal controllers. Dedicated voltage for the PCH internal logic core. +VCC_CORE Variable (~0.8V - 1.2V)