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Author Topic: Crazy fault in SD2000 detectors  (Read 3552 times)

woody

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Crazy fault in SD2000 detectors
« on: July 23, 2016, 01:22:04 am »
The detector is deaf as a post, it will pick up the side of a car and not much else.

First check the n channel fet near the coil connections, these fail due to metal migration in the semiconductor layers. 

Near the lm 394 ic on the input there is a 68 pf capacitor that is leaky, that is that it still measures like a capacitor but it starts becoming resistive, i have found this capacitor to fail on countless sd2000 detectors. It s located near he 4093 ic that controls the gate timing of the receive fets, it is used as a timing delay to give a small delay before turning on the fets after the end of the transmit pulse.