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                        Kenwood Service Centers

   Kenwood Service Corporation             Kenwood Service Center, East
   2201 East Dominguez Street              829 Lynnhaven Parkway, Suite 130
   Long Beach, California 90801            Virginia Beach, Virginia 23452
   Telephone 1-310-639-5300                Telephone 1-804-340-1702

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BULLETIN # 828
MODEL: TR-7800
SUBJECT: TR-7800 TONE PAD CONVERSION FOR 4th COLUMN FUNCTION
                                                        
     Users who desire ABCD control functions may be accomodated
     by an alteration to the Control unit and to the REV switch.
     This switch will then perform dual functions.
     
      1. Remove top and bottom covers, 4 screws each.
      
      2. To free the front panel, remove 4 screws securing the
         front panel bracket to the side frame.
         
     3. Unplug 5 multiconnectors from the Control unit along the
        front and left edges of the board.
         
     4. Remove 6 screws from the Control unit and swing the board
        over.
        
     5. Remove and save R51 22kn located between IC's Q19 and Q28.
         (Q28 pin 5).
         
     6. Resolder this 22k resistor to Q28 pin 5, and solder another
        22k resistor to Q28 pin 9. Using a short piece of hookup
        wire, extend these connections to the REV switch as shown.
     
     7. Connect a line from the center switch contact to the original
         feed point of R51, which is the B3 line.
         
      8. To reassamble, reverse steps 4 through 1.
      
     To operate the ABCD column, hold the REV switch IN and key the
     3,6,9 or # Keys. Normal 3rd column tones are supplied when the
     REV switch is not depressed. The receive REV function is not
     altered by this change.
     
     NOTE: This switch is a DPDT and may have both sets of contacts
     bridged. Free one set of contacts for this new function