How to Repair Dead 40-Inch China LED TV Power Supply Using CA-901 Module

 Repairing a dead power supply on a 40-inch China LED TV can be a frustrating challenge for electronics technicians. Standard replacement parts like the CA-888 (CA-888 REV:02) module often fail under heavier loads, leading to overheating and thermal breakdown.

This detailed technical guide explains how to diagnose a dead power supply board, test the main system board and backlight circuits safely, and install the robust CA-901 REV:02 power supply switching module to achieve a reliable, cool-running repair.

Technical Overview & Prerequisites

China LED TVs (such as 40-inch Smart TV models using integrated combo boards) frequently suffer primary side switching transistor/MOSFET burnout caused by line voltage spikes, degraded main filter capacitors, or poor thermal dissipation.

When repairing these boards, substituting the original switching circuit with a universal module is standard practice. However, selecting the correct module based on power ratings is crucial:

Module Model	Recommended TV Screen Size	Max Output Power	Thermal Stability	Primary MOSFET Type
CA-888	14 inches to 32 inches	~45W - 60W	Moderate (Heats up above 32")	TO-220 / Small Package
CA-901 REV:02	32 inches to 50 inches	~90W - 120W	Excellent (Heavy-duty Tab)	Heavy Duty Power MOSFET

Step 1: Initial Diagnosis and Isolation Testing

Before installing any new power module, you must confirm that the motherboard (system IC) and the LED backlight driver circuit are fully functional.

1. Visual Inspection: Inspect the primary side of the mainboard for burned SMD components, blown fuses, or swollen primary filter capacitors (400V/450V rating).

2. System Board Test (External 12V Supply): Connect an external regulated 12V DC power supply to the secondary side 12V rail (cold side filter capacitor terminals). Check if the standby LED turns on and if the system boots into its user interface (e.g., Smart TV menu/Android boot screen).

3. Backlight Test: Connect a dedicated LED backlight tester to the LED output header to verify that all LED strings inside the panel illuminate evenly without over-current protection triggering.

Step 2: Preparing the Board (Removing Damaged Components)

To prevent feedback interference or short circuits when introducing the CA-901 module, clean the burnt area on the primary side:

1. Desolder and remove the faulty primary switching MOSFET / Power IC from the board.

2. Remove any shorted SMD resistors or burnt diodes near the gate drive line.

3. Keep the main bridge rectifier, primary filter capacitor (300V DC rail), and the main high-frequency transformer intact.

By default, the CA-901 module is set to a 24V DC output configuration.

To convert the output from 24V to 12V, perform the following modification on the module board:

• Step 1: Locate the zero-ohm 0 ohm SMD jumper resistor on the PCB (typically positioned near the 24V label on the back side of the module).

• Step 2: Desolder and completely remove this 0 ohm resistor from its pads.

• Step 3: Short (solder bridge) the designated pair of pads located directly below it marked for 12V operation.

Removing this zero-ohm jumper reconfigures the internal voltage divider network on the module, stepping down the secondary regulated output from 24V to a stable 12V DC.

Step 3: Wiring Connection Guide for CA-901 REV:02

The CA-901 REV:02 module uses a 5-wire harness to integrate directly into the SMPS transformer primary and secondary feedback loops.

Wiring Pinout & Connection Guide

• 1. Red Wire (Drain / Primary Switching)

  • Where to connect: Connect directly to the Drain pin (D-Pin) connection of the original MOSFET on the primary (Hot) side of the main transformer (Chopper).

• 2. Black Wire (Hot Ground)

  • Where to connect: Connect to the Negative (-) terminal of the main primary filter capacitor (400V / 450V capacitor) on the primary side.

• 3. Yellow Wire (Secondary Main Output / 12V-24V Rail)

  • Where to connect: Connect to the positive output side (Cathode/Anode junction) of the main secondary rectifier diode on the secondary (Cold) side that supplies the 12V or 24V line.

• 4. White wire (Cold Ground)

  • Where to connect: Connect to the Negative (-) terminal of the secondary filter capacitor (Cold Side Ground) on the secondary output side.

• 5. Green wire (Feedback / Auxiliary VCC Supply)

  • Where to connect: Connect to the feedback optocoupler's line or the original IC's VCC line (9V–18V) on the primary side to enable automatic voltage regulation through the TL431 loop.

Step 4: Testing & Final Verification

1. Double-check all wiring connections for short circuits using a multimeter in diode mode.

2. Connect the board to AC mains supply via a series safety lamp board (100W bulb) to protect against accidental shorts.

3. Verify that the secondary voltage stabilizes at 12V DC.

4. Mount the heavy-duty metal tab of the CA-901 module securely onto the TV chassis or an adequate heat sink using thermal paste.

5. Power on the TV set completely and verify full display bootup and picture quality.

Conclusion & Benefits of Using CA-901

By replacing the unreliable primary switching circuit with the CA-901 REV:02 module, you eliminate the overheating issues common with smaller CA-888 modules on screen sizes above 32 inches. The dedicated heat tab and higher current tolerances ensure cool operation, prolonging the lifespan of the repaired LED TV.

Learn More :👉How I Fixed a Flickering 43-Inch Borderless Smart LED TV: The Hidden Connector Problem