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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 # 930
MODEL: TM-721A
SUBJECT: MICROCOMPUTOR LOCK-UP

Some early model TM-721A transceivers may malfunction when nearby 
transmissions, such as operating a handheld too close to the unit, enter 
the microprocessor reset circuit. As the RF energy enters the circuit, 
the microprocessor ceases to function which results in shutting off the 
sub-display, receiver, and transmitter. Adding a capacitor to the base of 
the reset switching transistor on the control unit will correct this 
condition. The following procedure will detail how to access the transistor.


REQUIRED PARTS:

C124 1000pF 50V CHIP CAPACITOR CK73FB1H02K

1. Disconnect the power supply and antenna from the transceiver.

2. Pull the Volume, Main squelch, and Main tuning knobs from the front panel.

3. Remove the top and bottom covers (12 screws). Do not damage the speaker 
   wires when removing the top cover.

4. Remove the silver colored screws from the front panel chassis (2 on 
   each side, 1 on top, and 1 on the bottom).

5. Carefully pull the front panel assembly out from the body of the 
   transceiver (do not disconnect any cables).

6. Remove the 2 brass colored screws from the top of the of the plastic 
   front panel.

7. Lift the 2 tabs on the bottom of the front panel and pull the panel 
   off the assembly. Do not loose the black shades positioned over the 
   Balance and Sub-squelch switches. Keep the switch assembly intact as 
   much as possible.

8. Straighten the display unit mounting clips and pull the display unit 
   from the control board (do not disconnect the cable).

9. Locate Q102 on the top right hand side of the control board (next to 
   the volume control).

10. Add a lOOOpF chip capacitor between the base of Q102 and ground (the 
    capacitor will physically be mounted between C123 and R141).

11. Assemble the transceiver by reversing the steps above.

Time required for this modification is 1.5 hrs or less.