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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 # 936
MODEL: TM-721A
SUBJECT: S-METER DEFLECTION DUE TO PULSE NOISE

When the TM-721A is operated mobile, strong ignition noise generated by
motorcycles may cause the S-meter to deflect on the VHF band. The ignition 
noise cannot be mistaken for a signal because the busy light does not 
come on, but the S-meter deflection may be distracting. Th following 
modification will prevent this occurrence.

PARTS REQUIRED:

10pF, 50V CHIP CAPACITOR CC41FCH1H100D 
0.47uF, 25V CHIP CAPACITOR C92-0003-05

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

2. Remove the top cover. Disconnect the speaker wires.

3. Unplug all connectors on the TX-RX (VHF) unit. Remove the 7 screws 
   securing the board to the transceiver and then remove the board from 
   the transceiver.

4. Desolder and remove C39 from the bottom of the board. Install an solder 
   a 10pF capacitor in place of C39 (Figure 1).

5. Add a 0.47uF capacitor from the junction of R39 and D11 to ground 
   (Figure 1). Install the TX-RX unit.

S-NETER ALIGNNENT

1. Apply power to the transceiver.

2. Set the transceiver to receive at 146.040NHz.

3. Inject a -1 dBu (0.45uV) signal into the VHF antenna connector.

4. Adjust VR2 on the TX-RX (VHF) unit to obtain an S-1 indication on 
   the display.

5. Increase the input signal to 30 dBu (15.8uV) and verify that all the 
   LEDs liqht.

6. Disconnect the signal generator. Turn the transceiver off. Install 
   the top cover (don't forget to plug in the speaker).

Time required for this modification is 1.0 hrs or less.