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Topic: How can I test Shift Registers? (Read 390 times) previous topic - next topic

eptheca

I have 8 x 74HC164 Shift Registers soldered in a circuit that had a short and some parts blew up.
I suspect that the SR's could be broken.
Is there a way to test them with a multimeter in the circuit?

Cheers, Hal

MarkT

Some things can be tested, but usually you follow the signals through the circuit and check they are
doing what is expected, step by step.

First check the board's power consumption is normal and no chips are getting hotter than you'd expect
(they are fried if so).
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kanishkaprasad

i dont know if im right please correct ! but try to measure the resistance of each pins compared to a new one so u can have assumption that its working or not !! but i might be wrong !! just said to help you in away !!

MarkT

Doesn't always work very well in a circuit.

You can probably check that protection diodes are working using the diode-test mode of the multimeter I
suppose, most CMOS inputs and outputs have protection diodes to ground and Vcc.  If you short Vcc to
ground then most pins will act as diodes to ground either way round - if its shorted that might be bad
(if nothing else in the circuit shorts it), if its open that's also bad (some pins don't have protection diodes
in some cases, you always have to double check with the datasheet really).
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srnet

A multimeter might indicate if a chip is faulty, but it might well not.

You need a scope or similar to check that the signals at inputs and outputs are as expected. A multimeter wont do that.
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