Computers which use a television as a monitor can produce a "snow" effect if the television set is not correctly tuned or improperly connected. This is visible as moving speckles on the display of varying severity, ranging from slight artifacts superimposed on an otherwise good image to a display consisting of nothing but noise.
  • First, check all leads and connectors for bad connections by wiggling the cable near the plugs. If in doubt, replace the cables.
  • Consult the documentation for the television for tuning instructions. For some older machines (notably the Sinclair ZX80 and ZX81) it can be difficult or impossible to obtain a good picture on modern televisions with digital tuners. In such cases an older set with analogue fine tuning is preferable. Some [wiki="TV Modulator"]modulator[/wiki]s provide some fine adjustment of their output by means of a [wiki]potentiometer[/wiki], which can help match the signal generated at the computer to that expected by the television.
  • If tuning the television does not provide a picture, or the picture is still imperfect, suspect the [wiki="TV Modulator"]modulator[/wiki] or related circuitry. Many machines can also be made to produce a [wiki]composite video[/wiki] signal with simple modifications, allowing them to be connected to modern displays by bypassing the modulator completely.