Monday, August 11, 2025

Fault Repair Professional Secrets Book

Top 10 Common LED TV Problems and How to Fix Them at Home

📺 Top 10 Common LED TV Problems and How to Fix Them at Home

By Imran Ashraf – Electronics Repair Guide

LED TVs are an essential part of every home, but like all electronics, they can develop faults over time. If your LED TV is giving trouble, don’t worry — many problems can be fixed at home with some basic tools and knowledge. Here are the 10 most common LED TV problems, their causes, and easy fixes.

1️⃣ TV Turns On but No Picture

Cause: Faulty backlight, damaged T-CON board, or loose LVDS cable.
Fix: Shine a flashlight on the screen — if you see a faint image, the backlight is faulty. Check LVDS cables. Replace LED strips or T-CON board if needed.

2️⃣ No Sound but Picture is OK

Cause: Audio IC failure, damaged speakers, or settings issue.
Fix: Check sound settings, test with headphones, replace speakers if necessary.

3️⃣ TV Stuck on Logo / Boot Loop

Cause: Corrupt firmware or faulty main board.
Fix: Update firmware via USB. If it fails, replace or repair the main board.

4️⃣ Remote Control Not Working

Cause: Dead batteries, dirty IR sensor, or faulty remote.
Fix: Replace batteries, clean IR sensor, test remote using mobile camera.

5️⃣ Vertical or Horizontal Lines on Screen

Cause: T-CON board failure or panel issue.
Fix: Reseat ribbon cables. Replace T-CON board if needed.

6️⃣ Colors Look Distorted

Cause: Faulty T-CON, gamma IC, or wrong picture settings.
Fix: Reset picture settings. Replace gamma IC if required.

7️⃣ TV Not Turning On (No Power)

Cause: Faulty power board or blown fuse.
Fix: Check fuses with a multimeter. Replace power board if needed.

8️⃣ Backlight Flickering

Cause: LED strips or power supply problem.
Fix: Replace LED strips. Check voltage output to backlight.

9️⃣ TV Turns Off by Itself

Cause: Overheating, faulty power supply, or software glitch.
Fix: Clean ventilation holes, update firmware, replace capacitors if needed.

🔟 HDMI Ports Not Working

Cause: HDMI IC failure or damaged port.
Fix: Try different HDMI cables. Replace HDMI IC if necessary.

🛠 Tools Needed for Bas

IF you want a complete LCD/LED TV screen voltage diagnosis guide that explains:

What each voltage is called
What its normal range is
Where to measure it
How to know which one is missing
How to fix it

Here’s the full technician-level explanation.

📺 LCD/LED TV Screen Voltage Diagnosis & Repair Guide

1️⃣ Understanding Screen Power System

The screen (panel) in an LCD/LED TV needs multiple voltages to operate, generated mostly on the T-CON board (or integrated into the main board in some TVs).

Typical main voltages:

Voltage Name	Symbol	Typical Range	Function
Panel VCC	VCC / VDD	3.3V – 12V (model-dependent)	Main power for logic circuits
VGH	Gate High	+22V – +32V	Turns ON TFT pixels (row selection)
VGL	Gate Low	–5V to –12V	Turns OFF TFT pixels
AVDD	Analog VDD	12V – 16V	Powers column drivers
VCOM	Common Voltage	~4V – 7V	Pixel reference voltage
Gamma Voltages	V1–V14	Stepped levels	Control grayscale accuracy
VREF	Reference Voltage	~1.2V – 3.3V	For ADC/DAC circuits in panel
LED Backlight Voltage	LED+ / LED–	20V – 200V (depends on strips)	Powers LED strips

2️⃣ Where to Measure Voltages

Main Panel Supply (VCC) → At T-CON input fuse (label F1/F100).
VGH, VGL, AVDD, VCOM → Near T-CON power IC (often marked VGH, VGL, VCOM on PCB).
Gamma Voltages → On Gamma IC pins (AS15, GM8284, etc.).
LED Voltage → On LED driver output (often part of power board).

3️⃣ Step-by-Step Voltage Testing

Step 1 — Check Panel VCC

Location: T-CON fuse input.
Normal: 3.3V / 5V / 12V depending on panel type.
If missing:
- Check main board MOSFET switch circuit.
- Replace blown fuse.
- Trace supply from main board regulator.

Step 2 — Check AVDD

Location: Output pin of T-CON DC-DC boost converter.
Normal: 12–16V.
If missing:
- Check T-CON boost IC (MP2363, RT8293, etc.).
- Test inductor & diode for shorts.
- Replace faulty IC.

Step 3 — Check VGH

Location: Marked pad on T-CON, or on ribbon to panel.
Normal: +22V – +32V.
If missing:
- DC-DC boost for VGH faulty.
- Check for short on gate driver IC in panel.
- Replace boost IC or repair short.

Step 4 — Check VGL

Location: Near same area as VGH.
Normal: –5V to –12V.
If missing:
- Negative voltage generator faulty.
- Check boost capacitor/diode.
- If shorted to ground, gate driver IC inside panel is bad.

Step 5 — Check VCOM

Location: VCOM test point on T-CON or panel ribbon.
Normal: Around ½ of AVDD (~5–7V).
If unstable/missing:
- Adjust in service menu or via T-CON potentiometer.
- Bad op-amp in T-CON may cause lines/flicker.

Step 6 — Check Gamma Voltages

Location: Pins of Gamma IC (AS15, etc.).
Normal: Gradual step-down voltages (V1 highest, V14 lowest).
If one step jumps abnormally:
- Gamma IC faulty → replace.

Step 7 — Check LED Backlight Voltage

Location: LED driver output on power board.
Normal: Depends on number of LED strips (e.g., 80V for 4 strips, 180V for 10 strips).
If missing:
- Driver IC or MOSFET faulty.
- Open LED strip → backlight won’t start.

4️⃣ Common Fault Symptoms & Missing Voltage Clues

Symptom	Likely Missing Voltage
TV on, backlight works, but no display	AVDD / VGH / VGL
White screen	Missing VGL or VCOM
Faint picture, needs torch to see	LED backlight voltage
Colored vertical lines	One Gamma voltage abnormal
Logo freeze	Panel VCC drops during boot

5️⃣ Quick Reference Voltage Table

Voltage	Range	If Missing → Check
VCC	3.3–12V	Fuse, MOSFET, regulator
AVDD	12–16V	Boost converter, diode, inductor
VGH	22–32V	Boost IC, gate driver short
VGL	–5 to –12V	Negative pump, short to GND
VCOM	~5–7V	Op-amp, adjustment
Gamma	Steps from AVDD to 0V	Gamma IC
LED+	20–200V	Driver IC, LED strips

6️⃣ Repair Tips

Always measure with TV powered ON and T-CON connected.
Use digital multimeter in DC mode.
If a voltage is present but drops after 1–2 seconds → load fault (short).
Isolate panel by disconnecting one ribbon at a time to see if voltages stabilize (panel half short).

If you want color-coded voltage diagram for LCD TV T-CON boards showing exactly where to put your probes and what voltages to expect — that makes real repairs much faster you need to buy my Printed Book Online it's a complete repairing course for your repair shop.

Order Now Book BY IMRAN ASHRAF

SOFTWARE SOLUTION