La-d401p Schematic Page

Look for the power-on sequence chart (usually found in the first few pages of the Compal PDF).

: Essential for fixing "no power" issues by showing the sequence from G3 (off) to S0 (fully powered). la-d401p schematic

| Symptom | Likely Cause | Diagnostic Steps | |---------|--------------|-------------------| | | Power not reaching board (blown fuse, broken J1) | Check continuity of J1 → F1 → D1; measure voltage after F1 | | LED flashes red | Over‑current or over‑temperature protection active | Measure voltage across R7 (over‑current) and TMP1 (temperature). Replace Q1 if it shows high Rds(on). | | Output voltage present but current low | Sense resistor R4 drifted high, or U2 lost offset | Measure voltage across R4 at a known load; replace R4 if > spec | | Oscillating output | Insufficient compensation (C4 too low) or poor layout (long gate trace) | Add small parallel capacitance (e.g., 4.7 nF) to the gate of Q1, shorten trace | | Excessive heat on board | Boost inductor saturated or MOSFET overloaded | Verify L1 inductance and current rating; check Q1 for overheating (use thermal camera) | Look for the power-on sequence chart (usually found

is a proprietary motherboard manufactured by Compal Electronics HP Spectre 13-v Replace Q1 if it shows high Rds(on)

Check for activity on the BIOS chip (often labeled 'U') pins 1, 2, 5, and 6. Where to Find the Schematic