It was observed when attempting lid up operation on 2024-02-06 that the brakes for each of the jacks were not operating correctly. It appeared that power was not being applied so the brakes were stuck in the engaged state. This ultimately resulted in issues with the lid up operation.

The issue was traced to relay A1 (the master brake power relay) not toggling as expected, despite the relevant control signals being present to try to enable it. This relay is located in the MCC-E 400V panel. Adjacent to the relay is fuse F4 which supplies the relay. This fuse was blown. The fuse was: English Electric CIS50. 50A rated, 600V, H.R.C. Form II. Replacements were ordered, however the part is obsolete due to its age. In the short term, a temporary workaround was implemented by installing a 30A fuse. This will be replaced when the spare fuses arrive.

The system was powered up again today (2024-02-07) and the brakes energized as expected. It appears that there is no issue. The root cause of why the fuse blew in the first place is unknown at this time. It was originally suspected that it was due to accidental mis-wiring of the brakes when they were reconnected after annual servicing, but if this was true, the fuse would have instantly blown again when relay A1 was energized. The best guess at this point is that the fuse failed due to age (it is likely around 60 years old).

This e-log will be updated if any further developments are made on this issue.