> The noise imunity of the 74LS164s seens to be very poor,
> as if I simply touch the clock line with the soldering iron, the
> displays/LEDs makes a random switch

Presumably you don't touch the clock line with clock signals
on it ?

I've had the same thing with the 164. I have a display that
uses 8 of them with a common clock line driven from one
PIC pin. The display goes mental if I touch the clock line with
even a scope probe. The answer for me was to reduce the
fan-out (which I assume is the problem and the probe just
tips the balance) by using the 8 gates in two 4081s to split
and buffer the clock signal from the PIC. A 74xx08 would
be a TTL alternative

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