La-d401p Schematic Access

Symptom: No LED, no 3V on power button. Schematic Fix: Find the TPS51285 (or similar) power controller. The schematic lists pin 7 (EN1) and pin 14 (ENTRIP2) as enable signals. Without those enable voltages (coming from the EC or a resistor divider), the IC won't produce the 3V/5V always-on rails. You can trace back exactly why EN is low.

Using the LA-D401P schematic, here is a workflow for common symptoms:

Symptom: Dead TV (No Standby Light)

Symptom: TV Clicks but Won't Turn On

| Symptom | Likely Cause | Diagnostic Steps | |---------|--------------|-------------------| | No laser output, LED indicator off | 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) | la-d401p schematic

Because multiple revisions of the LA-D401P exist, ensure you match the silkscreen on your physical motherboard.

Look at your board. It will say: COMPAL LA-D401P REV: 1.0 SAVE 332 DA0AM6BBA0 Symptom: No LED, no 3V on power button

The schematic for REV 1.0 is different from REV 2.0. Using the wrong revision will lead to wrong component locations.

If the laptop turns on and off repeatedly, the issue might lie in the "S0" state rails. The schematic reveals the sequence of Power Good (PG) signals. For example, you can check if the +3VALW rail reaches the EC (IT8226VG) and if the EC replies with RSMRST#. Symptom: TV Clicks but Won't Turn On |

Let's say +1.05V_S0 is missing.