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Replacing a 74ls14 with a 74ls04

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andybarrett1:
Hi All

I have a small circuit just for debouncing a pb switch into a PIC Micro. It currently has a 74ls14 (Schmitt Inverter)  in situ, I am fault finding and found one of its output was u/s. Thinking a 74ls04 is a basic inverter with same pinout I have replaced.

But then none of the outputs are changing states (should be high when switched) .... All are stuck low even through the pull ups on PIC pins.

Replacing again with a 74ls14 all is good ..... What might be reason for not liking the 74ls04.

Attempting to understand this

Andy

amyk:
There's a reason they make both a '14 and a '04... that circuit needs a Schmitt.

GopherT:
I thought the story was going to end differently. I thought you would realize you could denounce in software and eliminate the extra hardware.

andybarrett1:
Problem is I am a hardware guy in a software world...

I have since found putting a chip exactly the same back in works..... Any other chip fails even an equivalent ???

BR
Andy 

capt bullshot:

--- Quote from: andybarrett1 on February 19, 2019, 11:57:45 am ---Replacing again with a 74ls14 all is good ..... What might be reason for not liking the 74ls04.

--- End quote ---

Depends, need to see the schematic.
A 74HC14 or 74HCT14 might work as a drop-in replacement.

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