Power Distribution Board / Vacuum Controller Board
Power Distribution Board (PDB) - is both the primary distribution node for the the incoming power and the board that starts and controls the diffusion pump. The PDB is stuffed under the manifold, behind the electronics chassis (sheet metal where main board and I/O board are mounted). It is rare that this board dies, but it does happen.
The beauty of this board is that it fully controls the diff pump with or without the PC and Chemstation up and running. Get the manifold under vacuum and power on the MSD. This board will take over and turn on the diff pump when the vacuum is low enough and provide the "Diff Pump On and Hot" signal when appropriate. The board also provides a red led to indicate that the diff pump is powered on and running. You can see the red led through a one-half inch hole in the chassis back behind the smartcard near where the power cord comes in.
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