The Acer Aspire 5552, built on the Compal LA-6552P (PEW76/86/96) motherboard, represents a classic era of AMD-based mobile computing. Utilizing the AMD RS880M Northbridge and SB820M Southbridge architecture, this board is a staple for chip-level technicians. While robust, it is frequently seen on repair benches for thermal-related failures in the Northbridge BGA or power delivery issues within the ISL-controlled charging circuit. As a senior engineer at geniusmind4u.blogspot.com, I have analyzed this specific REV 1.0 (2010) board to provide you with the most accurate diagnostic roadmap.
Board Architecture & Technical Specifications
| Component | Specification / Identifier |
|---|---|
| Motherboard Model / ODM | Compal LA-6552P PEW76-86-96 REV 1.0 |
| Target Laptop Series | Acer Aspire 5552 / 5552G / 5252 |
| Chipset / CPU Architecture | AMD S1G4 Socket (Phenom II/Athlon II) + RS880M / SB820M |
| Super I/O (EC/KBC) | ENE KB926QF D3 |
| Key Voltage Rails & Coils | PL27 (+3VALW), PL28 (+5VALW), PL24 (+1.1VS), PL10/11 (+VCC_CORE) |
Real-World Motherboard Diagnostic Procedures
1) Input Power Stage & DC-IN Protection Circuit
On the LA-6552P, the primary power rail +19VB is managed by the ISL6251AHRZ (PU1) charging IC. If the laptop is completely dead with no lights, first check the voltage at PR1 (Current Sense Resistor). If +19V is missing there, inspect PQ1 and PQ2 (AO4407A P-Channel MOSFETs). These are often held closed if ACIN (Pin 2 of PU1) is below 3.2V or if the IC detects a short on the main rail. Ensure DCIN (Pin 24) is receiving the adapter voltage through the protection diode PD1.
2) Standby Rail Generation & Thermal Short Testing
The +3VALW and +5VALW rails are generated by the RT8206B (PU4) buck converter. Before replacing the IC, measure the resistance to ground on PL27 and PL28. A low resistance (under 50 ohms) on PL27 often indicates a punctured Southbridge (SB820M) or a shorted ENE KB926QF EC controller. If the LDO regulator +3VLP (Pin 7) is missing, the EC will never initialize, preventing the power button from responding. Note that in this AMD platform, the Northbridge 216-0752001 is a high-heat component; if the board has power but no display, check the +1.1VS rail at PL24, as failure here is common.
3) Power-On Sequence & Signal State Tracking
For a "Power On, No Display" symptom on this Compal board, track the following sequence using your oscilloscope or multimeter:
- EC_ON: High (3.3V) sent from KB926 to enable the ALW rails.
- RSMRST#: Check at Pin 100 of U20; it must transition from 0V to 3.3V to alert the Southbridge that power is stable.
- CLK_PCI_SB: Ensure the 14.318MHz and 32.768kHz crystals are oscillating.
- BIOS Communication: Probe Pin 1 (CS#) of the SPI Flash U31. If there is no data activity during the first 2 seconds of power-up, the AMD Northbridge is likely failing to fetch the reset vector, or the BIOS firmware itself is corrupt.
Download Schematic & Boardview Files
Direct download link. Verified schematic / boardview archive.
Professional Repair Assistance
Explore our technician resources:
- 🛠️ Diagnose No-Power & Short-Circuit faults step-by-step: Interactive Laptop Diagnostic Lab
- 🛒 Original Replacement Motherboards & IC Components: Official Spare Parts Mega Store
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