Cable Tester Uses Quad Latch

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This circuit was designed to allow
microphone cables or other cables to be easily tested for intermittent
breaks that can often be difficult to find using a multimeter. The
circuit can test cables with up to four cores. Both switches used in the
circuit are momentary contact push-buttons and it can run from a 9V
battery, in which case the 7805 regulator can be omitted. To test a
cable, connect it between the two sockets and press switch S2 which
resets all four latches in IC1, setting them low. This turns on all four
LEDs.

Cable Tester Uses Quad Latch

Cable Tester Uses Quad Latch

A good connection for each core of the cable will mean that the relevant
Set inputs of the latches (pins 3, 7, 11 & 15) will be pulled high
and the appropriate LED will remain on. A
broken connection in the cable will result in the relevant Set input
being pulled low by the associated 10kΩ resistor and the so the LED
will be off. Because the circuit latches, it is easy to pinpoint even
the smallest breaks by simply flexing and twisting the cable up and down
its length until one of the LEDs turns off. To test different types of cables, simply connect appropriate sockets in parallel with or in place of the XLR sockets.
Author: Ashley Dawson – Copyright: Silicon Chip Electronics