HT go off due to the active external interlock

Issue

The HT went off during data acquisition

Environment

Krios G3i

Resolution

These are possible resolutions for the issue:

• Replace IPB

Cause

These are possible causes for the issue:

• external interlock triggered; IPB defective

Details

The HT went off during data acquisition in the mid-night without any user's interruption.
It could be turned on but went off again when moving the compustage.

Action:

1. Pilz sensors on the HT cable and on the column have been swapped.No help.
2. power-cycle the tool ,No help.
3. VGIB board has been replaced. No help
4. The relay on the HT tank has been checked. Function good.
5. VGIB is already replaced and issue not fixed
6. The BSDR is never activated during a shut down. 
7. IPB interlocks are working as it should be
8. VCBT working OK according to the TAD tests
9. Check the X24 connector on the HTTMB of the HT tank. OK
10. Check the X43 connector on the HTTMB of the HT tank. OK
11. The cable connection on the VCBT also looks fine.
12. In manual mode, open Vcp, close Vac --> HT does not switch off
13. In manual mode, open Vac, close Vcp --> HT does not switch off
14. In manual mode, open Vac and Vcp both --> HT drops out.
15. Vcp and Vac singal go to the VGIB. Since VGIB is already replaced and blacker shutter are never triggered we suspect VCBT.
16. new VCBT board has been mounted. it does not solve the issue
17. Replace IETM, no help.
18. Coil impedance of the K2 relay is slightly below spec, order HT Tank Subrack
19. Order a HT PIB board.
20. HTPIB Board Test pass
21. HTCB Board Test pass
22. IETM Interlock Test pass
23. HT Generator Test (Dummy plug) pass
24. HT Generator Test (HT Cable) pass
25. Human Safety Circuit test pass
26. When the connector X6 was disconnected from IPB, the HT stays on after the column valve is open.
27. When X 6 was connected back to IPB, HT would switch off again.
28. The HT stays on after IPB was replaced. The issue has been resolved