Direct answer
For the LG B3 OLED TV, built-in menus versus every external input separates panel/backlight faults from HDMI/source problems. First, display the TV menu and a built-in app in a dark room.
What this covers
- LG B3 OLED TV (OLED55/65/77B3*)
- LG TV; OLED/QNED/LCD panel, webOS year, HDMI bandwidth and Magic Remote vary by model.
- The specific fault this record addresses: has sound but no picture
What it does not cover
- ×The same symptom on a different LG product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
The panel or T-CON board has failed
What separates it Sound is normal, the screen is completely black, and a torch held close reveals nothing at all underneath.
How to confirm An OLED has no backlight, so this symptom points at the panel driver or the panel itself. Confirm the set is genuinely on — check for a menu overlay by pressing a menu button, which will appear even with no source signal if the panel is alive.
- 2
The set is on the wrong input
What separates it A black screen with sound coming from a different source than expected, or no picture after another device was connected.
How to confirm Cycle every input deliberately rather than relying on auto-detect, which frequently lands on an empty port.
- 3
The picture has been turned off deliberately
What separates it Sound continues normally and the screen is black, with no fault at all. Several sets have a picture-off, screen-off or audio-only mode intended for listening to music.
How to confirm Check the manual for this model's picture-off mode and how to exit it. It is easy to select by accident from a remote shortcut, and it presents exactly as a dead panel.
- 4
The source device is outputting a resolution or format the set cannot display
What separates it One source is black while others are fine, often after a console or player was set to a new resolution or HDR mode.
How to confirm See hdmi-no-signal. A set that cannot handle the incoming format may pass audio while showing nothing.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- Whether a torch held close to the dark screen reveals a faint image underneath — on an LED/LCD set this single test identifies a backlight failure.
- Whether pressing a menu button produces a visible on-screen menu, which proves the panel can still display something.
- Whether the problem affects every input or only one.
- Whether any picture-off or audio-only mode has been enabled.
Press a menu button and look for an on-screen menu
ReversibleA visible menu proves the panel and its driver work, which moves the problem to the input or source rather than the display.
Cycle through every input deliberately
ReversibleAuto-detect frequently settles on an empty port and presents as a dead screen.
Check for a picture-off or audio-only mode and exit it
ReversibleSeveral sets have one, it is easy to trigger from a remote shortcut, and it looks exactly like a failed panel.
Arrange service for a confirmed panel or driver-board fault
ReversibleAn OLED has no backlight, so this is the panel or the board driving it. Neither is user-serviceable, and on a large set an OLED panel replacement often costs close to a new television — get a quote before authorising the work.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- OLED55/65/77B3*. LG TV; OLED/QNED/LCD panel, webOS year, HDMI bandwidth and Magic Remote vary by model.
- Panel
- 2023 entry OLED (regular OLED glass, no evo brightness boost) — the dimmest 2023 LG OLED. Still perfect-black and self-emissive, so picture complaints are gradation/processing, not backlight.
- Smart platform
- webOS 23 with the Magic Remote — same app store, update path and AirPlay 2 / Miracast screen share as the C3/G3.
- Gaming / HDMI — IMPORTANT port limit
- Unlike the C3 and G3, only TWO of the B3's four HDMI ports are full HDMI 2.1 with 4K 120 Hz; the other two are HDMI 2.0. A console or PC that will not do 4K 120 Hz or VRR on a B3 is very often plugged into one of the two HDMI 2.0 ports — move it to a 2.1 port first.
- Symptom boundary
- This record covers LG B3 OLED TV when it has sound but no picture. A different symptom on the same hardware, or this symptom on a different LG product line, has its own record with its own causes and its own cited source.
Stop boundary
When this stops being a self-service repair
Continuing past any one of these costs more than the repair saves — in safety, in warranty, or in evidence a technician needs.
- !Unplug the set for a burning smell, smoke, or visible damage or bulging at the rear panel.
- !Do not disassemble a television to inspect a backlight — the panel is fragile, and large sets carry stored charge in the power supply.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. LG Support publishes this as "TV and home theater support". Official LG television manuals, webOS support, diagnostics and repair entry point. What that article does not carry is the model boundary — it is written for a product line, and OLED55/65/77B3* is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
My PS5/Xbox won't do 4K 120Hz on my LG B3.+
Check which HDMI port it is in. On the B3, only two of the four HDMI ports are full 2.1 with 4K 120 Hz and VRR — the other two are HDMI 2.0 and cap out lower. This is different from the C3 and G3, where all four are 2.1. Move the console to one of the 4K-120-capable ports (they are labelled in the manual), use a 48 Gbps cable, and turn on Game Optimizer.
Is the flashlight test useful on an OLED?+
No — an OLED has no backlight at all. Each pixel makes its own light, so there is nothing behind the panel to fail and nothing for a torch to reveal. On an OLED, sound with a completely black screen points at the panel or its driver board instead.
Could this just be a setting?+
It can be. Several televisions have a picture-off, screen-off or audio-only mode meant for listening to music, and it can be selected accidentally from a remote shortcut. It looks exactly like a dead panel. Check the manual for this model's version before assuming hardware.
Does this answer apply to every LG model?+
No. It is scoped to OLED55/65/77B3*. LG TV; OLED/QNED/LCD panel, webOS year, HDMI bandwidth and Magic Remote vary by model.
What should I record before troubleshooting no picture or black screen?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing no picture, black screen. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Unplug for smoke, arcing, a cracked panel or heat.
Answer for the exact device and software version shown above.