BeoSystem 3 MK1: No Sound via S/PDIF AV5 with LG TV

[Alexey Malyugin]

Hello, dear community! I need help with my BeoSystem 3 MK1 (Type No. 9604, Serial No. 20953799).

Setup:

LG 55QNED80T6A (2024)- HDMI ARC/Toslink – coaxial (Tubon 002) –  AV5 SPDIF IN BS3.

Output: 2× BeoLab 8000 (PL1/PL2 Left/Right Front) – bought them for their incredible beauty, but sound only works via RCA.

Video: DVI-OUT BS3 – monitor.

I have a screenshot from the monitor available

V.OPT 2, BS3 test tones work (speakers green).

Attempts:

Settings: Connections → Sound Input = SPDIF (AV5/AV6), Video = HDMI-A, STORE.

Sources: LG (PCM 48/16), PC (Realtek S/PDIF, 44.1/48 kHz) → coaxial/AV5/AV6.

Converters: ARC extractor, PALMEXX (optical→coax), BSP CA-50 (Coax OUT).

Workaround: LG Toslink → BSP CA-50 → RCA → BeoLab (LINE) — sound works.

Tried V.OPT 1/0, but switching doesn’t work (only 2 available).

Issue: No external sound via AV5 (speakers orange), though Sound System shows PCM 2.0. In monitor settings, AV4, AV5, AV6 are not visible. Service menu: IIC1 -84: ACK_MIS, errors 00F8. AV5 is visible in Connections but not activated. Video works stably. I have a screenshot from the monitor available.

Questions: How to activate AV5 for sound? Is an audio-only mode (V.OPT 0) possible? Need advice on settings or diagnostics. I can share the monitor screenshot if needed. Thank you!

 

• This topic was modified 16 minutes ago by Alexey Malyugin.

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