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                             K E N W O O D
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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 # 843
MODEL: TR-8400
SUBJECT: Sub-audible Encoder Installation
                                                        
     When installing a sub-audible encoder in a first-lot radio,
     change the Tone switch power source from the 8C (common) to
     the 9T (transmit) line. This will prevent the encoder from
     distorting the receiver when the Tone switch is ON.
     
     Procedure
     
     1. Remove the bottom cover (2 long screws, rear, 3 short
         screws, front) and unplug the speaker.
         
     2. Cut the GRAY lead to the Tone switch wiper one inch from
         the switch. Tape-insulate the long lead to the harness.
         
     3. Connect the switch wiper to the Mic connector , pin 5.

     4. Install the encoder, connect the speaker, and replace the
        bottom cover.
     
     For complaints of distorted sub-audible tone in a first-lot
     unit, replacing components and readjusting the PLL will
     reduce or eliminate distortion.
     
     Procedure
     
     1. Remove the top cover (4 screws).
     
     2. Remove the rubber conductive shield.
     
    3. Remove the aluminum cover from the PLL unit X50-1670-xx
         (17 scews).
         
     4. Unplug connectors J2-J6.
     
    5. Remove 11 screws and 2 threaded studs securing the PLL
         printed circuit board. Shift the board to the rear, then
         swing up and to the right.
         
     6. Use Wikit or a desoldering tool to remove and replace:
     
                       Component     was   replace with (vicinity of Q7)
                       R30           12k   18k 1/4 w
                       R31           820   390 1/4 w
                       C47           6.8pF 15pF Tantalum (observe polarity)
                       C48           6.8pF 15pF "
              
         Note: Don't create solder-bridges or lift the foil.
         
     7. Reverse steps 5, 4, 3 to partially reassemble.
     
     8. Perform the PLL adjustment listed in the Service Manual,
        Page 24, item 2.
         
     9. Reverse steps 2 & 1 for final assembly.