Why do picture snow and instability appear in a normal DA setup?
In several instances, completely unexpected picture snow, interference and instability occur. It may happen in a solid studio setup, even when using high quality equipment and good sources. The effect shows up on the screen as noise, zigzag lines, picture bending and “flagging” and a host of other unwanted, very visible types of interference. It may happen in all different video formats – Composite, Y/C or Component. There may be several reasons that contribute to the interference, and they have to be checked one by one in order to detect the cause and eliminate it: Sometimes, low quality audio cables of excessive length and cable capacitance cause the audio circuitry to oscillate, injecting interference into the whole system. To check this, disconnect the audio cables and watch the picture. Breakdown of the shield (screen) of one of the coax cables at one end may cause interference pickup and oscillations. Disconnect each cable in turn to find the faulty one. Loose contact of a connec
