the short search - or the search for the short

the short search... elektor June 1985 the short search... ...or the search for the short Printed circuits are particularly prone to mechanical defects, especially when they contain many thin tracks. Finding the mechanical cause of a malfunctioning memory board, for instance, is certainly a time consuming job! Every conscientious hobbyist of course, checks his circuits carefully after completion, both visually and with a multimeter. But what do you do when you detect, say, a short-circuit and cannot locate it visually? A simple test consists of removing all ICs from their holders in the suspected area and injecting an audio signal of about 1 kHz into the doubtful printed circuit tracks. The current consequently flowing through the tracks causes an electro- magnetic field. This field can be detected with an old (but working!) recording head from a cassette or tape recorder: the out- put of the head is applied to a small audio amplifier terminated in a miniature loudspeaker. When the...