7474 Chip Replacement QUESTIONS

From: Jack Peacock <peacock_at_simconv.com>
Date: Thu Mar 12 18:01:29 1998

>Instead, Q is low and NOT Q is high which is the reverse of
what SHOULD
>be the case. What's the deal? Bad 7474? Or is my thinking
SCREWED UP?
>
>IF my thinking is correct and my suspicion that the 7474 is
bad, is it
>safe to replace it with a 74LS74? A friend of mine and I had a
long
>conversation about what you can replace with what and I've
forgotten
>what he told me about that.
>
considering the low speed of a 6800, an LS (or even an HCT)
should work...but, are you sure it isn't the case of a fast
pulse on the D input when CLK is hit (on the falling edge if
memory is correct)? and you aren't seeing it (using a logic
probe or a triggered scope)? did you check the voltage in to D?
maybe it's in no mans land (i.e. around 2v). Maybe its the IC
driving the flip flop D input thats bad, or a fast pulse is
hitting the R* input

Anyway, I'd take it out and put in a socket if you think its
most likely cause
    Jack Peacock
Received on Thu Mar 12 1998 - 18:01:29 GMT