1. The cables were suspected to be faulty. Then engineers tested the cables, and found that the cables were normal by consulting relevant documents and removing the cables.
2. Engineers learnt that the problem was with the alarm driving of the MITU board, by consulting relevant documents and referring to the corresponding R&D engineers for help. Version A of the PCB of the MITU board does not support alarm driving. Version B of the PCB of the MITU board support alarm driving.
3. The BOM codes of the PCB of version A and the PCB of version B were the same, which were 03034709. Thus, version A and version B of the PCB could be distinguished only by their respective hardware versions.
Three methods are available to distinguish the two versions:
l ) Check the front panel of the board.
In the case of the PCB of version A, there are two indicators on the front panel, which are the "RUN" indicator and the "ALM" indicator. In the case of the PCB of version B, there are three inidcators on the front panel, which are the "RUN" indicator, the "ALM" indicator, and the "ACT" indicator.
2) Check the manufacturing date of the board.
Boards manufactured in January 2007 or later are all of the PCB version B or higher. All these boards support alarm driving.
3) Check the silkcreen of the PCB on the lower right of the MITU board.
Remove the board, and then you can see a line of words printed on the PCB. If the printed words are "MITU PCB Ver.A", it indicates that the PCB on this MITU board is of version A. If the printed words are "MITU PCB Ver.B", it indicates that the PCB on this MITU board is of version B.