L3+ hash rate is low or a hash board is faulty

Please try to reload the firmware:

https://shop.bitmain.com/support.htm?pid=00720170915192851224mJ36J1ap066E

Run the miner for 20 minutes after reloading the firmware.

Please check the power supply and controller first.

To check the power supply, you can use a well-functioning power supply to test the miner. If you don't have another PSU, you can also check by switching the cables between the hash boards. If the problem is with the cable, the power supply may be faulty.

To test the control board, switch the controller cable between the hash boards. If the same hash board shows the issue then the hash board is faulty. If the issue follows the cable then the controller may be faulty.

If it is still not resolved, please test each hash board separately to determine which hash board has failed.

To test each hash board separately: keep the power supply connector of one hash board connected to the control board cable, and disconnect the cables on the other two hash boards. With the operation of the miner, you can see the status of the connected hash board.

Here is more detail:

https://zeusbtc.com/articles/asic-miner-troubleshooting/1050-how-to-test-antminer-hash-board-one-by-one

On the miner status screen defective chips are displayed as "xxx", "---" or " ASIC≠60.