Diagnosis
The "No Signal" error on your TV when attempting to use the JBL Bar 300 indicates a breakdown in the HDMI-CEC (Consumer Electronics Control) handshake. This is not a hardware failure of the HDMI port, but rather a software "lock" where the TV and the soundbar have lost their synchronization protocols. This typically happens after a firmware update on the TV or a sudden power surge that leaves the HDMI controller in a frozen state, preventing the ARC (Audio Return Channel) from routing audio from the TV back to the soundbar. You can confirm this is a handshake issue if the soundbar still functions via Optical cable or Bluetooth, but fails specifically on the HDMI ARC port. If the TV does not recognize the soundbar in the "Audio Output" or "Speaker List" menu, the CEC link is broken. Because the JBL Bar 300 relies on a specific voltage signal to trigger the switch from Bluetooth/Optical to HDMI, any instability in the TV's HDMI-CEC handshake will result in the "No Signal" or "No Device Connected" message.
How to Fix It
To resolve a handshake failure, you must perform a "Cold Boot" of the entire hardware chain to clear the volatile memory of the HDMI controllers. Follow these exact steps:
- Turn off the TV and the JBL Bar 300 using their respective power buttons.
- Physically unplug the power cords for both the TV and the soundbar from the wall outlet. Do not simply use the remote; the capacitors must be fully discharged.
- Disconnect the HDMI cable from both the TV's HDMI (ARC/eARC) port and the soundbar's HDMI OUT (ARC) port.
- Wait exactly 3 full minutes. This ensures the HDMI handshake cache is completely wiped.
- While the power is still off, plug the HDMI cable back into the TV's designated ARC/eARC port and the soundbar's HDMI port. Ensure the cable is seated firmly; a loose connection of even 1mm can break the CEC pin connection.
- Plug the TV back into the wall power and turn it on.
- Once the TV is fully booted to the home screen, plug the JBL Bar 300 into the wall power and turn it on.
- Using the TV remote, navigate to Settings > Sound > Output and select Receiver (HDMI).
If That Didn't Work
- Reset the JBL Bar 300 to Factory Defaults: While the soundbar is powered on, press and hold the Volume + and Bass - buttons simultaneously for about 3 seconds. The light bar will flash, indicating a reset. This clears any internal software glitches preventing the ARC handshake.
- Toggle TV CEC Settings: Navigate to your TV's system menu and disable the CEC feature (Samsung calls it Anynet+, LG calls it SimpLink, Sony calls it Bravia Sync). Turn it off, wait 30 seconds, and turn it back on. This forces the TV to re-scan all HDMI ports for compatible ARC devices.
- Swap the HDMI Cable: If the original cable has suffered a pin failure (specifically pin 13, which handles CEC), the soundbar will never be detected. Replace the cable with a High-Speed HDMI cable (Version 2.0 or 2.1) rated for 18Gbps. Avoid using older "Standard" HDMI cables.
- Test a Different HDMI Port: Some TVs have multiple HDMI ports, but only one is labeled ARC or eARC. Verify the cable is plugged into the specific port marked with these labels. If your TV has multiple ARC ports, try switching to the other one to rule out a dead port.
Heads Up
- Avoid Power Strips: Plugging the soundbar into a cheap power strip can cause voltage drops that trigger HDMI handshake drops. Plug the Bar 300 directly into a wall outlet whenever possible.
- Firmware Updates: Use the JBL Headphones app to check for soundbar firmware updates. Many ARC stability fixes are delivered via these updates.
- TV Sleep Mode: If this happens frequently, disable "Quick Start" or "Fast Boot" in your TV settings. These modes often put the HDMI ports into a shallow sleep that prevents the soundbar from waking up correctly.
- Cable Routing: Do not run the HDMI cable parallel to high-voltage power lines or AC adapters, as electromagnetic interference (EMI) can disrupt the low-voltage CEC signal.