Seems obvious, but isn't VTL helping you troubleshoot this?
What is causing false tube faults in VTL MB450 Series III?
I’m having trouble with one mono vtl amp which frequently signals a tube fault (red faults,green fault) requiring 2-4 reboots. The tubes were purchased recently through VTL. The tube(s) responsible for the warning alert changes. After repeated restarts the amp performs as expected.The second amp with new tubes as well does not have this problem. Any thoughts? Thank you