Zenith PRO 841x/851x

      >> Introduction 
      >> Layout and Setup Tips 
      >> Focus Block Replacement 
      >> CRT Tube Replacement 
      >> Manuals / Downloads 

Video Processor

The PC board shown below is the video processor board. It contains almost all of the set’s low level signal components including all b/w and color circuits, the on screen menus, memory and H and C drive. Despite the complexity of this board, it is quite reliable, and many assumed problems with this board actually end up being elsewhere in the set. Again, other than the menu adjustments, there are no controls to tweak on this board.

Interconnect and focus modulation boards

There is a small CRT interconnect board located behind the convergence power supply. It is simply a board that feeds various common signals to each CRT. I’ve never had one of these boards fail.
 

Focus modulation board

Next to the interconnect board is the focus modulation board. This board is only found on the PRO 851 set. It gives the set slightly better corner and edge focusing over the older models.

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