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. 

There are only 5 boards (assemblies) in the HP 5971 and HP 5972 MSD.  Over the next few blog entries we will assist you in troubleshooting each of these modules.

O-Rings for the HP/Agilent can be purcased directly from Agilent  but they can be rather expensive.  Now that the HP 5972 and HP 5971 is so old, finding the right o-rings can be problematic.

If you have an HP 5971 or Agilent 5972 MSD and you can't get the diff pump to turn on there are only a few possibilities.  1)  You have a massive leak and the diff pump controller board won't allow the diff pump to turn on.  2)  The DC power supply in the MSD is dead and can't run the pump controller board,   and 3)  The diff pump heater is dead.  

HP 5971 and HP 5972 Mass Spectrometers have difussion pumps and on the frame of the diffusion pump are two sensors.  A   Too Cold Sensor, the bottom (white wires) and the Too Hot Sensor, the top (red wires).   The signal from the sensors report to the startup and run electronics of the Power Distribution Board.

The Horror of it all!   Customers call when they get this error and exclaim all manner of frustration.  They've often spent several days trying to recover from this error - including re-booting, deleting and reloading the software, re-configuration of the instrument.  Violence is often part of the equation and sometimes I think drinking is also involved.  This particular error is very harsh and very un-forgiving.   In fact, the only way to recover from this insidious error is to reboot your PC!  Sometimes you even have to pull the plug.  Yikes!