The short answer
Shine a bright torch at the screen at an angle in a dark room. If you can faintly see a picture, the panel and processing are fine and the backlight has failed, which is a repairable fault. If there is nothing at all, the problem is further upstream, and the input, cable and source need checking first.
Sound with no picture is a useful symptom, because it tells you that the TV is receiving and decoding the signal correctly. The audio arrived. That eliminates a large part of the chain immediately, and what remains divides neatly into a few possibilities.
The torch test
Darken the room and turn the TV on
Play something with sound so you know it is running.
Shine a bright torch close to the screen at an angle
A phone torch works. Hold it about 10cm away and move it slowly across the screen.
Look for a faint image
If you can make out the picture, menus or channel logos, the panel is working and the backlight is not.
If there is nothing at all
Move on to the input and cable checks below, then the main board possibilities.
A failed backlight means either the LED strips or the driver board that powers them. On many sets this is a common and fairly inexpensive repair, and replacement LED strips are widely available. It is within reach for a confident DIY repairer on some models and is fiddly work involving removing the panel, so many people have a shop do it.
TVs contain a power supply that stores charge after being unplugged. If you open one, treat the power board as live and avoid touching it. If that is not a risk you want, this is a repair shop job and the cost is usually modest against replacing the set.
If the torch test shows nothing
Check the obvious input causes
- Wrong input selected, which produces silence on the picture and sometimes sound from a different source such as a soundbar still playing.
- A cable partially out. HDMI has no latch, and audio and video use different pins, so a partially seated cable can deliver one and not the other. Push both ends in firmly.
- A failing HDMI cable, particularly at 4K. Swap it for a known-good one.
- A dead HDMI port. Try another port on the TV.
- A resolution the TV cannot display. A source set to an unsupported mode can output audio while the TV rejects the video. Most devices revert after fifteen seconds if you do not confirm; if yours is stuck, reset its video output, which usually has a button combination for safe mode.
Check whether the TV’s own menu appears
This is the key diagnostic. Press the Menu or Settings button on the TV’s own controls. If the menu appears, the panel, backlight and processing are all working, and the problem is the input or source. If the menu does not appear but you can hear the navigation sounds, the fault is in the display chain.
What fails inside a TV
- Backlight LEDs or their driver: the most common cause of this symptom by a wide margin, and repairable.
- The T-Con board, which drives the panel. Usually produces distorted images rather than none, though total failure happens. It is a plug-in board and among the easier replacements.
- The main board, which handles processing. Less likely when audio still works, since audio usually passes through the same board.
- The panel itself, which is effectively unrepairable. A cracked or failed panel means the set is finished, because a replacement panel costs more than a new TV.
The order above is roughly the order of likelihood, which is good news: the most common cause is also the cheapest fix.
Search your TV’s exact model number with the words backlight or no picture. Panels and boards are shared across many brands, and common faults on a given chassis are well documented, often with a specific known-failed component. That search frequently tells you the answer and the price before you call anyone.
Before assuming hardware
- Power cycle properly. Unplug from the mains for a full minute, press and hold the TV’s power button for ten seconds while unplugged to discharge, then plug back in. This resets the internal state and occasionally restores a set that appeared dead.
- Check for a software update if the menu is visible. Rare, and it does happen that a firmware bug causes a black screen on specific inputs.
- Disconnect everything and power on with nothing attached. A faulty source device can hold the HDMI negotiation in a failed state.
- Check any energy-saving or eco sensor setting, which in extreme cases dims the backlight to nearly nothing in a dark room.
Is it worth repairing?
Roughly speaking: a backlight repair on a mid-size set is usually a fraction of the cost of replacement and worth doing on any TV less than about eight years old with a panel you are happy with. A main board replacement is more variable. A panel fault is not worth repairing at any age.
Get a quote before deciding, and ask specifically what part has failed. A shop that will name the component is a shop that has diagnosed it.
Why can I hear sound but see nothing at all?
The TV is receiving and decoding the signal, so the failure is in the display path: most often the backlight, sometimes the board that drives the panel. The torch test distinguishes these.
Is a failed backlight worth fixing?
Usually yes on a reasonably modern set. LED strips are inexpensive and widely available, and the labour is the main cost. It is generally far cheaper than replacing the television.
Could it just be the HDMI cable?
Yes, since audio and video travel on different pins. A damaged or partially seated cable can carry sound while failing on video. Swapping the cable is the cheapest test available.
Why does the picture come back if I tap the TV?
That points at a loose connector or a cracked solder joint, often on the backlight driver board. It will get worse, and it is a specific and usually repairable fault.
Does this happen to OLED TVs too?
OLED has no separate backlight, so the torch test does not apply. Sound with no picture on an OLED points at the panel driver or main board, and is generally a more expensive repair.
In order
Torch test first, because it splits the problem in half in thirty seconds. Then check whether the TV’s own menu appears, which tells you whether the display chain works at all. Swap cables and ports, try another source, and do a proper power cycle. If the panel is fine and the backlight has failed, get a quote, because that is the cheap end of TV repair.
