Digital signal in my circuit is too noisy
For 74LS, you need VDD bypass capacitors across 7/14 or 8/16 of each IC. With no more than 1/8&quot; leads to the bypass cap, 0.01UF or 0.1uF.
And ensure the GROUND wire between your two trouble points is WIDE, such as copper braid.
And, finally, insert 100 ohms at the signal source of your troubled wire. Maybe 150 or 220 ohms.