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The message itself rules out half the possibilities
If your TV is displaying the words “No Signal”, the panel, the backlight and the TV's software are all working — it is drawing that message for you. Nothing inside the television is broken. The fault is upstream: the wrong input is selected, the source device isn't awake, or the cable or port between them isn't carrying video. Check those three, in that order.
Applies to: Any TV that displays a No Signal, No Source, or Weak Signal message — Samsung, LG, Sony, TCL, Hisense, Vizio, Philips and Panasonic included. Menu names differ by brand and model year; the paths below name the common ones.
When does the message appear?
“No Signal” is one of the more useful error messages a TV produces, because it tells you what is already working. A TV that can render text has a functioning panel, backlight, and main board. That narrows the search to the input chain, which you can work through without tools. Change one thing at a time and check the screen after each.
It says No Signal on every input
Is the source device actually powered on rather than asleep?
Check the sourceOnly one HDMI input says No Signal
Does the same device work on a different port?
Test port and cableIt appeared after the TV or device slept
Does reconnecting in the right order bring it back?
Redo the handshakeIt's on antenna or cable TV, not HDMI
Have the channels been retuned recently?
Check the tuner1. Confirm you're on the input you think you are
This sounds too simple to be the answer and it frequently is. Press the Source or Input button and step through every input in turn, pausing a couple of seconds on each — some TVs need a moment to detect a signal before they give up and show the message again. Note which inputs say No Signal and which show a picture, because an input that works proves the TV's video path is fine.
Then confirm the physical port matches the label. HDMI 2 on the menu is the socket printed HDMI 2 on the back, and on wall-mounted sets it is easy to have counted wrong from the front. Samsung's guidance is to make sure the TV is set to the same source the device is plugged into — if the box is in HDMI 1, the TV has to be on HDMI 1.
If your TV has a One Connect Box or a separate breakout box, the sockets are on that box rather than the panel, and its own connecting cable is one more link that can fail. Check it is firmly seated at both ends.
2. Make sure the source device is awake, not just on
A standby light is not the same as a running device. Cable boxes, consoles and streaming sticks all drop their video output when they sleep, and the TV correctly reports no signal. Wake the device with its own remote and watch for its own activity light to change.
Laptops and PCs deserve particular attention here. LG's guidance calls out sleep and hibernation directly: a laptop that has slept often needs the HDMI cable disconnected and reconnected before it will re-detect the display and start driving it again. Waking the laptop alone is frequently not enough. On Windows, pressing the display-switch key combination or Win+P and choosing Duplicate or Extend will also push output to the TV.
If the source is a streaming stick powered from the TV's own USB port, try a mains adapter instead. USB ports on TVs often cut power in standby or supply less current than the stick needs, which produces intermittent no-signal that seems to follow no pattern.
3. Reconnect in the right order and power-cycle
HDMI negotiates a handshake between the TV and the source when the connection is made, and a failed handshake produces exactly this message. The order matters, and Samsung's documented sequence is worth following precisely: disconnect the power cords of the TV and the external device for at least 10 seconds, reconnect them, then connect the HDMI cable to the external device first and to the TV second.
Sony's version of the same step is to unplug the TV's power cord — around two minutes for its Android TV and Google TV models — and to disconnect other attached hardware, including USB drives and other HDMI devices, so that one misbehaving device cannot hold the input in a bad state. Bring things back one at a time.
Anything between the source and the TV is a common cause: an AV receiver, a soundbar with HDMI passthrough, a switch, or a long extender. Connect the source directly to the TV, bypassing that box completely. If the picture returns, the middle device or its HDCP handling is the problem, not the TV or the source.
Turning the TV off with the remote is not a power cycle — it stays energised in standby. Pull the plug from the wall for the full interval, or the handshake state you're trying to clear survives.
4. Isolate the port from the cable
Move the same device and the same cable to a different HDMI port. If it works there, the original port has failed — a contained, common fault, and one that needs no further diagnosis. If it still says No Signal, keep the port and change the cable instead. Changing one variable at a time is what makes this conclusive.
Cable quality genuinely matters at higher resolutions. LG recommends using a genuine HDMI cable of version 2.0 or later, and a cable that was adequate for 1080p can fail at 4K or at higher refresh rates while appearing undamaged. Runs longer than about five metres are a frequent cause — test with a short cable at the TV before concluding anything about the television.
Both major brands can test the cable for you rather than making you guess. On Samsung, go to Settings → Support → Device Care → Self Diagnosis → HDMI Troubleshooting and check the connected ports in turn. On LG, use HDMI Check under Quick Help in the TV's settings, which reports whether the cable is faulty. A failed cable test means buying a cable, not booking a repair.
Samsung
Settings → Support → Device Care → Self Diagnosis → HDMI Troubleshooting, then check each connected port in turn.
LG
Quick Help → HDMI Check in the TV's settings reports whether the connected HDMI cable is faulty.
5. If it's antenna or cable TV rather than HDMI
A No Signal or Weak Signal message on a broadcast input is a different problem, and the HDMI steps above don't apply. Samsung describes the message as meaning the TV is connected to a source but is not receiving a strong enough signal from it to display. Start at the aerial lead: check it is screwed in at the wall and at the TV, and inspect the connector for a bent or pushed-back centre pin.
Then re-run the channel scan. Broadcasters re-allocate frequencies periodically, and a tuner holding a stale channel list will report no signal on channels that have simply moved. The option usually sits under Settings → Broadcasting, Channels, or Tuner, named Auto Tune, Auto Program, or Channel Scan.
If only some channels fail while others are fine, that points to signal strength rather than the TV — weather, a moved aerial, a corroded outdoor connection, or a splitter dividing the signal too many ways. Many TVs show a signal strength meter in the same settings area, which is worth checking before calling anyone.
6. When it really is the TV, and what to tell support
By this point the remaining possibility is a failed HDMI port or the board behind it. The evidence for that is specific: a device that works on one port and not another, with the same cable, after a full power cycle. A single dead port on an otherwise healthy TV is a normal failure and is repairable, though on older sets the board cost is often close to the value of the television.
Rule out a firmware issue first if you can still reach the menus, since HDMI handshake bugs are a genuine category of problem that manufacturers fix in updates. Check for a software update before arranging service, and only consider a factory reset after that — it clears every setting and sign-in and cannot repair a failed port.
When you contact support, give them the tests rather than the symptom. Say which inputs fail and which work, whether a second device fails on the same port, whether the same device works on a different port, what the built-in HDMI cable test reported, and whether a full power cycle changed anything. Those five answers separate a cable from a port from a source device, and they are what turns a vague call into a specific repair.
Frequently asked questions
Why does my TV say No Signal when everything is plugged in?
Most often the TV is on a different input from the one the device is plugged into, or the device is asleep rather than on. After that, the usual causes are a failed HDMI handshake — fixed by unplugging both at the wall for at least 10 seconds and reconnecting the cable to the device first — and a cable or port that has stopped carrying video.
Does a No Signal message mean my TV is broken?
Almost certainly not. The TV has to be working to display that message at all: the panel, backlight and main board are all fine. It means the television isn't receiving usable video on the selected input, which puts the fault in the input selection, the source device, the cable, or the port.
Why does only one HDMI port say No Signal?
Either that port has failed, or the cable plugged into it has. Separate the two by moving the same device and cable to another port: if it works there, the port is at fault; if it doesn't, change the cable while keeping the port the same. Samsung and LG both include a built-in HDMI cable test that settles it.
My laptop shows No Signal on the TV. Why?
Laptops stop driving an external display when they sleep or hibernate, and often won't resume without the HDMI cable being disconnected and reconnected — LG's guidance calls this out specifically. Waking the laptop by itself is frequently not enough. On Windows, Win+P and selecting Duplicate or Extend will also push the output back to the TV.
Do I need a new HDMI cable?
Possibly, and it's cheap to rule out. LG recommends a genuine cable of HDMI version 2.0 or later, and a cable that worked at 1080p can fail at 4K or higher refresh rates without looking damaged. Runs over about five metres are a frequent cause. Test with a short cable at the TV before concluding anything about the television itself.
What if it says No Signal on antenna channels rather than HDMI?
That's a tuner or aerial problem and the HDMI steps don't apply. Check the aerial lead is secure at both ends and its centre pin isn't damaged, then re-run the channel scan — broadcasters move frequencies, and a stale channel list reports no signal on channels that have simply relocated.
Sources and review notes
Checked on . Compiled by Glitchary from manufacturer troubleshooting documentation. Menu paths vary by brand and model year — check the manual for your exact model. The port and cable swap tests are diagnostic checks rather than a guarantee of repair, and any work inside the television should be done by a qualified technician. Glitchary is independent of Samsung, LG, Sony, and the other manufacturers named here.