Colour Test Pattern Generator

50 EE December 1988 COLOUR TEST PATTERN GENERATOR from an idea by G. Kleine A PAL-compatible colour video source that supplies a number of test patterns for aligning television sets. A test pattern generator is virtually in- dispensable for troubleshooting in tele- vision sets because it supplies a video signal that is known to be stable, and thus easily displayed and synchronized on an oscilloscope. Moreover, the instru- ment allows the user to trace a fault in a TV set or other video equipment by selecting the most appropriate test pat- tern (e.g. a cross-hatch for convergence testing, or a dot pattern for focusing ad- justment). The test pattern generator discussed here is based on three integrated circuits: a pattern generator (ZNA234E from Fer- ranti), a video matrix chip with DAC in- puts (LM1886) and an associated video modulator (LM1889). The latter two chips are manufactured by National Semiconductor. Block diagram The general set-up of the pattern gener- ator is shown in...