Hello,
We have issue with SN74HC04 part, the component with marking HC04 15K G4 ACRF , this component simply does not work, we do not have the ability to perform a more detailed analysis. Whether this hexa inverter is not working at all, or there is a timing issue, we can't say that. Products with marking HC04 9CK G4 CLHV are working perfectly. Please investigate what could be the reason, I need your feedback to return not working parts.