LG SC9S Soundbar Keeps Dropping eARC Audio on LG UP77 TV (Have to Reboot TV Each Time)

[Pranay Mokida]

Setup

• TV: LG 55UP77 (UP7750)

• Soundbar: LG SC9S (purchased ~1 month ago)

• Connection: HDMI eARC using the original high-speed cable that shipped with the soundbar

• Firmware: Both TV and soundbar are fully updated (checked again today)

Issue
Whenever I start any video—whether it’s streaming apps, HDMI input, or a USB movie—the SC9S plays for a minute or two, then suddenly loses connection. Audio instantly falls back to the TV’s internal speakers, and the TV acts like the soundbar no longer exists on the eARC port. The soundbar display still shows “eARC” (sometimes flips to “OPT/ARC” for a second), but no sound.

Temporary Fix
The only thing that gets audio back is power-cycling the TV (standby isn’t enough; full reboot required). After that, the bar reconnects… until the next random dropout. This can happen multiple times during a single movie, which is a great way to kill the vibe.

What I’ve Tried

1. New HDMI 2.1-certified cable (same result, so original cable seems fine).

2. Disabled Quick Start+ and Simplink in the TV settings, then re-enabled.

3. Factory-reset both TV and soundbar.

4. Tested ARC instead of eARC—works, but no Atmos and same occasional dropout.

5. Plugged the soundbar into a different power outlet (in case of power spike).

Observed Patterns

• Dropouts happen sooner with Dolby Atmos or DTS content, but even stereo YouTube videos eventually cut out.

• No obvious heat buildup; bar is in open air, front facing.

• Happens whether soundbar is wall-mounted or on its stand.

Questions for the Hive Mind

1. Anyone else seeing eARC instability with the SC9S on the UP77 series?

2. Could this be a handshake timing bug on the TV’s HDMI board?

3. Any hidden service-menu tweaks or firmware betas worth trying?

4. Should I just RMA the bar, or is the TV the real diva here?

Appreciate any insight—my couch and I thank you in advance!

[tomatowarden]

Update:
Still haven’t found a permanent fix. What I’m doing for now is just toggling eARC off → on in the TV’s settings whenever the issue pops up. Once I do that, the soundbar stays stable and I’m not getting random HDMI drops anymore. Not ideal, but it beats power-cycling the TV every time.