Connecting the set-top box to your TV, and fixing "no signal"
4 min read · Updated 31 July 2026
A modern television connects to the box with a single HDMI cable. If the screen says "no signal" or stays black, the most likely cause by far is that the TV is showing a different input, not that anything is broken — press the source or input button and step through until you find the one the box is plugged into. Older televisions without HDMI use the round red, white and yellow AV sockets instead, and will show standard definition whatever the box is capable of.
The normal case: one HDMI cable
One cable carries both picture and sound. Plug it into any HDMI socket on the television, note the number printed beside that socket, and select the matching input on the TV.
That socket number is worth remembering. Almost every "the box has stopped working" call turns out to be a television left on the wrong input after something else was plugged in.
Working through "no signal"
Take these in order before assuming a fault:
- 1Check the light on the front of the box. No light at all means it is not powered — check the adapter at both ends and the wall switch.
- 2Press the source or input button on the TV remote and cycle through every input, pausing on each one.
- 3Reseat the HDMI cable at both ends. It should click home rather than sit loose.
- 4Try a different HDMI socket on the television, in case one port has failed.
- 5Restart the box: unplug it at the wall, wait thirty seconds, plug it back in and let it boot fully.
Older televisions without HDMI
Sets with only the round red, white and yellow sockets connect using an AV cable instead. Yellow carries the picture, red and white carry the sound. The television then needs to be set to its AV input rather than an HDMI one.
An AV connection is standard definition by nature. An HD box connected this way still works and still receives HD channels, but the picture that reaches the screen is standard definition. If sharper pictures are the point of the upgrade, the television is the limiting part, not the box.
When the picture works but the sound does not
Check the mute and volume on both remotes. The set-top box and the television each have their own volume, and one muted while the other is turned up is a common and confusing combination.
If sound goes through a soundbar or amplifier, make sure it is on the right input too. Where the television passes sound onward, an HDMI socket marked ARC is usually the one to use.
Questions people ask
My TV says "no signal" but the box light is on. What now?
Almost always the input. Press source or input on the television remote and step through every option slowly — HDMI 1, HDMI 2 and so on — pausing a couple of seconds on each. If none shows a picture, reseat the cable and try a different HDMI socket.
Will an HD box improve the picture on my old TV?
Only up to what the television can display. Connected over AV sockets, the picture is standard definition regardless of the box. The box is still worth having if you plan to change the television later, but it will not sharpen the current one.
Does a more expensive HDMI cable give a better picture?
No. HDMI is digital — the picture either arrives intact or visibly breaks up. A working inexpensive cable and a working expensive one produce an identical image at the lengths used in a living room.
Can I connect the box to two televisions at once?
Only to show the same channel on both. For different channels in different rooms you need a second box — see watching on more than one TV.