These are possible resolutions for the issue:
- Replace FREF
These are possible causes for the issue:
- FREF defective
- Beam breathing was found at different HT levels
- FSE checked HT cable from acc side and cleaned the cable. Have the EV flushed 5 times
- HT Tank was checked and Ibleeder was within spec
- TAD showed that GUN defector X&Ywith coil has error. See attachments.
- Lower HT results in bigger instability, BSDR replacement was done previously
- According to WI 103566 section 1.2 the next step would be opening acc
- Accidentally FSE found that after hot swapping FREF beam became stable. And the issue was fixed by replacing FREF.
When board test has error in TAD, check the values in txt file and check how much difference it has from the spec. Carefully judge if the board is indeed defective or not.