Phones
No Signal Lg Tv HDMI
If your LG TV displays a 'No Signal' error on an HDMI input, the cause can range from a simple handshake glitch to a damaged HDMI port or main board failure. Here is how to test your connections and isolate hardware issues.
Symptoms
- LG TV displays 'No Signal' or 'Check Signal Cable' message on active HDMI input
- Audio plays through connected speakers or optical out, but screen remains blank
- Screen flickers intermittently before dropping HDMI signal entirely
- Input selection menu shows the HDMI port as greyed out or disconnected
- Flickering horizontal lines, snow, or screen noise appears on the HDMI source
- Turning on connected devices fails to trigger TV input auto-detection
Quick troubleshooting
Step 1
Perform an HDMI Cold Reset (Flea Power Drain)
Unplug the LG TV power cord from the wall outlet and disconnect all HDMI cables from the TV ports. Press and hold the power button on the physical TV frame for 30 seconds to drain residual board electricity. Reconnect the HDMI cable firmly, plug the TV back in, and power on the source device before switching the TV input.
Step 2
Swap Cable and Test Alternative HDMI Ports
Disconnect your HDMI cable and inspect both ends for bent pins, physical debris, or cracked plastic casing. Plug a known-working High Speed or Ultra High Speed HDMI cable directly into HDMI 1 or HDMI 2 instead of ARC/eARC ports. Avoid using right-angle adapters, switches, or extension cables during this test to rule out passthrough degradation.
Step 3
Toggle HDMI Ultra HD Deep Color Settings
Navigate on your LG TV remote to Settings > All Settings > General > Devices > HDMI Settings. Toggle 'HDMI Ultra HD Deep Color' off or set it to standard mode for the affected input port. This resets signal bandwidth handshake protocols that often fail with legacy devices or standard USB-C to HDMI adapters.
Step 4
Verify Source Output Resolution and HDCP Compatibility
Connect the source device to a secondary monitor or another TV to verify it outputs video properly. Lower the output resolution setting on the source device to 1080p at 60Hz and disable HDR before re-plugging it into the LG TV. If video appears at lower resolution, your primary HDMI cable lacks bandwidth for 4K HDR passthrough.
Step 5
Update webOS Firmware or Execute System Reset
Ensure your LG TV is connected to Wi-Fi, then go to Settings > All Settings > General > About This TV and check for webOS system updates. If updates do not resolve the missing signal or if inputs remain greyed out, perform a system reset via Settings > General > Reset to Initial Settings. Note that this clears customized picture settings.
Likely causes
- HDCP handshake failure or CEC software freeze between LG TV and source device
- Loose, bent, or damaged physical pins inside the LG TV HDMI port
- Degraded or non-compliant HDMI cable failing to transmit full bandwidth
- Faulty main board HDMI controller IC or damaged multiplexer on the LG TV
- Corrupted LG webOS firmware or incorrect HDMI Ultra HD Deep Color settings
What's going on
When an LG TV shows a 'No Signal' or 'Check Signal Cable' screen across one or all HDMI ports, it means the TV's main board is not receiving or decoding a valid video stream from your connected device. This issue can stem from a temporary software handshake bug, a damaged HDMI cable, incorrect webOS picture bandwidth settings, or hardware damage on the main board's HDMI controller IC.
Whether you are connecting a gaming console, streaming box, laptop, or a mobile device via HDMI adapter, signal failures are frequently repairable at home without replacing the entire display.
Symptoms people notice
- 'No Signal' floating box: The TV screen displays an active input prompt but fails to show video.
- Black screen with audio: Sound streams through the TV speakers or soundbar, but the screen stays dark.
- Greyed-out input: The LG home launcher shows the HDMI port as disconnected even when a powered device is plugged in.
- Intermittent flashing: The image appears for a few seconds, flashes to black, or displays digital noise/snow before losing signal.
- Resolution error: 'Invalid Format' appears when changing display modes on a connected source.
Likely causes
- HDCP Handshake Freeze: Software timing mismatch between the LG TV webOS and the source transmitter.
- Defective or Low-Bandwidth HDMI Cable: Damaged internal wiring or inability to carry 4K/HDR signal bandwidth.
- Damaged HDMI Port Pins: Physical pins inside the TV port bent, pushed back, or broken from mechanical strain.
- HDMI Ultra HD Deep Color Mismatch: High-bandwidth color settings enabled on a port connected to a standard 1080p source.
- Main Board HDMI IC Failure: Power surges or ESD damaging the HDMI multiplexer chip on the LG motherboard.
Quick checks first
Before taking apart hardware, rule out configuration glitches with these fast checks:
- Cold boot power drain: Unplug the TV wall plug and hold the physical power button on the TV chassis for 30 seconds. Re-plug and power on.
- Try another HDMI port: Move the cable from HDMI 1 to HDMI 2 or HDMI 3 (avoiding eARC ports initially).
- Bypass adapters and switches: Plug the cable directly from your device into the TV without soundbars, AV receivers, or HDMI switchboxes in between.
- Test source device: Connect your source device to another screen to confirm it is outputting video.
For additional setup and connection walk-throughs, check our complete /guides library.
When it's a real repair
If performing a factory reset and swapping cables does not bring back video—or if all HDMI inputs show 'No Signal' across multiple known-working devices—you are likely facing a physical board or port failure.
Physical indicators of a hardware repair include:
- HDMI ports that feel loose, wiggle excessively, or show visible pin corrosion inside the jack.
- 'No Signal' occurring immediately after a lightning storm, power outage, or sudden power surge.
- All HDMI ports failing simultaneously while internal webOS apps stream video and audio normally.
In these scenarios, replacing the LG TV main board or reflowing/soldering a replacement HDMI port socket is required. Explore common display board symptoms on our /problems page.
DIY vs professional repair
Replacing an LG TV main board is one of the most straightforward DIY repairs for TV hardware. The main board is accessible by removing the rear panel screws and disconnecting ribbon cables and wire harnesses. Replacement main boards are widely available using the exact part number printed on your TV's board barcode.
However, micro-soldering an individual HDMI port connector onto the existing board requires fine-tip soldering gear, hot air rework stations, and board-level diagnostic skills. If you aren't comfortable replacing internal circuit boards or performing soldering, seeking assistance through LML Experts or opting for a board replacement service is the safest path.
Next steps
- Check your TV's exact model number on the rear label (e.g., OLED55C1PUB or 55UP7000PUA).
- Follow our detailed disassembly and safety guides in the /guides section to safely remove the TV back cover.
- If you need hardware advice or board matching assistance, post your symptoms in our /community forum.
Next steps
This often involves: HDMI Port Repair. Try the DIY guide if you're comfortable opening the device. Still stuck? Browse related problems for similar symptoms.
