The error code C-1028 on a Minolta Dialta 520 photostat machine typically indicates a problem with the paper feed system.
Based on your description, it seems that you have already replaced the PWB-B Board and checked all jacks, but the problem persists. In this case, there could be a few other potential causes of the error.
- Paper feed motor
- Main control board
- Gears or other parts in the paper feed system
- Paper feed sensor
Regarding the Bet Pin, it could be the name of a specific pin on the PWB-B board or in the paper feed system, but without more information about the specific location or context it is hard to say exactly what it is referring to.
It is recommended to consult the service manual of the machine, or contact the manufacturer or a professional technician for further assistance. They will be able to diagnose the issue and provide the necessary steps to fix it.