The Acer Predator 15 (G9-591G), built on the Compal P5NCN/P7NCN motherboard architecture, is a high-performance gaming machine that demands a robust power delivery system to support its Intel Skylake-H CPU and NVIDIA GTX 900M series GPU. As a senior engineer, I frequently see these boards in the lab with thermal-related power failures or high-side MOSFET breakdowns in the VGA core section. This guide provides the technical roadmap for diagnosing this specific Compal-designed PCB.
Board Architecture & Technical Specifications
| Feature | Specification / Component |
|---|---|
| Motherboard Model / ODM | P5NCN_P7NCN R1.0 (Compal) |
| Target Laptop Series | Acer Predator 15 G9-591G / G9-592G |
| Chipset / CPU Architecture | Intel HM170 PCH / Skylake Core i7-6700HQ |
| Super I/O (EC) Controller | ITE IT8587E (Compal Interfaced) |
| Charging IC | TI BQ24780S (Hybrid Power Boost) |
| Key Voltage Rails | +19VB, +3VALW, +5VALW, +1.2V_DDR4, +VCC_CORE, +VGA_CORE |
Real-World Motherboard Diagnostic Procedures
1) Input Power Stage & DC-IN Protection Circuit
The P5NCN board uses a BQ24780S (PU301) charging controller. If the laptop is completely dead with no lights, first verify the 19V rail at PR302 (current sense resistor). If 19V is missing, check the gates of the dual N-channel isolation MOSFETs PQ302 and PQ303. For these to conduct, the BQ24780S must output approximately 25V on the ACDRV (Pin 4). This requires ACDET (Pin 6) to be between 2.4V and 2.8V, derived from a resistor divider off the DC-IN jack. If ACDRV is low, check for a short to ground on the main B+ rail (+19VB) before replacing the controller.
2) Standby Rail Generation & EC Initialization
Unlike older boards with a single 3V/5V combo IC, this Compal design often utilizes discrete buck converters. Locate PU401 (+3VALW) and PU402 (+5VALW). For these rails to activate, the ITE IT8587E must be powered (VCC on pin 11/33/96/125) and the EC_ON signal must be high. If +3VALW is present but the laptop won't trigger, check the 32.768kHz crystal (Y2) and the RSMRST# signal. In the Predator series, the EC also manages the dual-fan PWM logic; a failure in the thermal sensing circuit (U55/U56) can sometimes prevent the S0 state transition as a safety measure.
3) GPU (+VGA_CORE) & Power-On Sequence Analysis
Gaming-specific failures on the P5NCN often involve the GTX GPU power phases. Measure the resistance to ground on PL1101, PL1102, and PL1103. A healthy Maxwell/Pascal GPU should show 0.8Ω to 2.5Ω depending on the chip variant. If you find 0Ω, the high-side MOSFETs (e.g., PQ1102) are likely shorted, potentially sending 19V directly into the GPU core. Always verify the ALL_SYS_PWRGD signal at the EC before assuming a CPU/GPU fault; this signal confirms that all secondary rails (+1.0V_VCCST, +1.2V_DDR, +1.05V_PCH) are stable.
Download Schematic & Boardview Files
Direct download link. Verified schematic / boardview archive.
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