"GTAW root/hotpass and cap". If you only welded three passes on a 5/8" plate, there is your problem. Need more info. Filler metal brand, welding parameters, by pass, What code are you working to, what are the impact requirements. Typically with GTAW you can swing a dead cat and get good CVN's. Need as much info as you can give. gmastsko, the poster says they are using the GTAW process.