nid your HELP ASAP!! 24 secs shot clock

https://www.electro-tech-online.com/attachments/24s-jpg.4492/

the diagram is in the link.. our problem is when the digit 4 counts down and reaches 0 the digit 2 also become 0. to be more specific if the countdown reaches 20 the next output should be 19 but its not its 00.. where must be the problem??

When the first 74ls192 reaches 0 the second 74ls192 is at the very same time trying to change from 0 to 1. The second action does not happen fast enough and the 4078 sees both 0's for a moment. It passes this through the 1k to the reset inputs.

Solution is to put a latch such as 74ls74 after the 4078 so it waits for the next clock before making a final reset.