The checklist, in the order that finds it fastest
“No Signal” means the TV is fine but nothing is arriving at the input it is showing. Nine times out of ten the fix is in the first three steps.
Is the source actually on?
Obvious, and still the number-one cause. Cable boxes fall asleep, streaming boxes lose power when a wall switch controls their outlet, and consoles go into rest mode. Wake the device first, then judge the TV.
Match the input to the port
Look at which HDMI number the cable is physically in, then press Input/Source on the remote until the TV shows exactly that. A TV parked on HDMI 2 while everything is plugged into HDMI 1 produces a perfect, permanent No Signal.
Reseat the cable — both ends
Unplug the HDMI at the device end, plug it back firmly, then do the TV end. Half-seated HDMI is invisible to the eye and notorious after any dusting or furniture move.
The 30-second power drain
Turn off TV and source, unplug both from the wall, wait 30 seconds, reconnect — then power the source first, TV second. This forces the HDMI handshake to renegotiate from scratch and clears the majority of stubborn cases.
Swap the port, then the cable
Move the cable to a different HDMI port on the TV (and select that input). Still dead? Try another HDMI cable — a certified high-speed one. Cables fail more often than either device.
Black screen but the sound still plays?
That specific symptom — audio without picture, or a screen that flashes on and off — is usually a failed copy-protection handshake (HDCP), not a broken TV. The devices are refusing to trust each other. The cure: unplug everything in the chain from power for a full minute with the HDMI cables disconnected, reconnect, and power up. If you have a splitter, switch or adapter between the device and the TV, take it out of the chain and go direct — those break the protection chain more than anything else.
A “Mode Not Supported” message is a different animal: the source is sending a resolution the TV cannot show. Drop the source’s output to 1080p in its settings and step back up from there.
Cable and satellite have their own reset
Spectrum: unplug the receiver for 60 seconds and replug — then be patient, a full reboot with guide data can take 15–20 minutes. DIRECTV: press the red reset button (on the side of the receiver or behind the access-card door), or unplug for 15 seconds; give it a full five minutes before judging. And a cabling note from the field: passive HDMI runs get unreliable past about 25 feet — and for 4K at 120Hz, past about 9 feet without a certified Ultra High Speed cable. Long wall-concealed runs that “mostly work” are usually a cable-grade problem, which is exactly the kind of thing we fix inside walls for a living.
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Quick answers
It says No Signal only on my 4K/120Hz console.
That's a bandwidth problem, not a broken console. 4K at 120Hz needs an Ultra High Speed certified cable (look for the certification label with a QR code) and one of the TV's full-bandwidth HDMI ports — many TVs only have one or two. Check the console is in the right port.
My Samsung TV can test this itself, right?
2022-and-newer Samsungs, yes: Settings → Support → Device Care → Self Diagnosis has HDMI Troubleshooting and signal tests. Older sets don't have it — the checklist above is the same thing done by hand.
It fixes itself when I unplug the TV, then comes back days later.
A handshake that keeps failing points at one weak link: most often the cable, next the splitter/soundbar it passes through, occasionally one dying HDMI port. Move ports and swap the cable before blaming either device.
Does the No Signal problem mean my wall-concealed cable failed?
Sometimes, and it's worth ruling out cheaply: run a spare HDMI outside the wall between the same two devices. If the picture comes back, the in-wall run or its couplers are the fault — we can usually re-pull a better cable through the same path.
TV shows No Signal on every input, even ones with nothing plugged in.
Empty inputs showing No Signal is normal — that's just what an empty input says. The question is only whether the input with your device shows it. If genuinely every connected device is dead on every port, then it is TV-side and worth a call.