I bought a Joust boardset declared 100% working.

When I tested it  all the coin inputs didn’t work

I ran the test and infact they were all activated

I was not worried because  I was sure it was the 6821P PIA on the romboard.

After replacing it didn’t fix the problem.

Looking at the schematic there are also some 4066 CMOS chips involved.

I desoldered the one used by the three coins inputs and after testing it on my programmer it was declared good.

I decided to add a socket and test another one on board

Luckily the problem was fixed and it turns  out my programmer is not reliable in testing CMOS devices.