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World of Ham Radio 1997
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==============================================================================
K E N W O O D
>>> A M A T E U R R A D I O S E R V I C E B U L L E T I N <<<
==============================================================================
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
==============================================================================
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.