HT Can’t Start,Gun dialog shows “External interlock”

Issue

HT cannot start，Gun dialog shows “External interlock”

Environment

Krios G3i

Resolution

These are possible resolutions for the issue:

• Replace VGIB

Cause

These are possible causes for the issue:

• Defected VGIB cause external vacuum interlock

Details

1. FEG is normal, but HT cannot start.
2. Almost all HT TAD tests failed on “HT on conditions” or “check HT and AUX are switched off”
3. Gun dialog shows “External interlock”
4. PILZ position was verified
5. K1 on IETM is the vacuum interlock relay, follow this path and found that VCBT is working properly, but VGIB is not generating output voltage back to IETM  
6. Replace VGIB and the issue was fixed