The Compal LA-4494P (KALG0) is a classic AMD-based motherboard architecture found primarily in the Acer Aspire 5535 and 5235 series. As a senior engineer, I often see these boards on the bench for 'No Power' or 'Power On, No Display' symptoms. This board utilizes the AMD RS780M Northbridge and SB700 Southbridge chipset, a combination known for significant thermal cycles that can lead to BGA solder fatigue or component degradation in the power delivery phases. In this guide, we will break down the power rails and signal logic using standard Compal nomenclature to help you pinpoint faults with precision.
Board Architecture & Technical Specifications
| Parameter | Details |
|---|---|
| Motherboard Model / ODM Part Number | Compal KALG0 LA-4494P Rev: 1.0 |
| Target Laptop Series / Form Factor | Acer Aspire 5535, 5235 / 15.6" Multimedia |
| Chipset / CPU Architecture | AMD Turion X2 / Athlon (Socket S1) + RS780M / SB700 |
| Super I/O (EC/KBC) Controller | ENE KB926QF-D3 |
| Key Voltage Rails & Switching Coils | +3VALW (PL5), +5VALW (PL6), +1.1V_NB (PL10), +VCC_CORE (PL8, PL9) |
Real-World Motherboard Diagnostic Procedures
1) Input Power Stage & DC-IN Protection Circuit
On the LA-4494P, the 19V rail (B+) is managed by the ISL6251 (PU1) charging IC. If the laptop doesn't power on at all, start by measuring the voltage at PR3 (current sense resistor). If B+ is missing, inspect the isolation MOSFETs PQ1 and PQ2. Specifically, check the ACSET pin (Pin 2) of PU1; it must be around 1.2V to 2.0V for the IC to drive the gates of the input MOSFETs. If PACIN is low, the EC will not receive the ACIN signal, preventing any further power sequencing.
2) Standby & Secondary Rails Generation
The +3VALW and +5VALW rails are generated by the TPS51125 (PU4). Even before pressing the power button, you must verify the LDO voltages: +3VLP (Pin 8) and +5V_REF. If the coils PL5 (+3VALW) or PL6 (+5VALW) show a low resistance to ground (< 200 ohms), suspect a shorted ceramic decoupling capacitor or a faulty Southbridge (SB700). Note that the +3VALW rail powers the ENE KB926QF EC; without this, the power button signal (ON/OFFBTN#) will never reach the chipset.
3) Power-On Sequence & Signal State Tracking
When the power button is pressed, the EC triggers EC_ON, which enables the secondary rails. For AMD Griffin/Puma platforms like this, the sequence is critical: The EC releases RSMRST# to the Southbridge, then the SB700 should respond by pulling PM_SLP_S3# and PM_SLP_S5# high. If the board spins the fan but gives no display, check PL10 (+1.1V_NB). A common failure point on this board is the RS780M Northbridge chip. Before reflowing/reballing, always perform a 'BIOS Clean' by flashing U18 with a known good dump, as the SB700 frequently corrupts the SPI ROM data during thermal instability.
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
