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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 # 925
MODEL: TM-3550A
SUBJECT: NOISY TRANSMIT

In some early model TM-3530A transceivers transmit noise may be generated 
as the unit warms up. The following procedure will reduce the noise.

1. Disconnect the power cord and antenna.

2. Remove the top and bottom covers.

3. Replace L3 on the Compound unit (part number L15-0308-05). 
   Before soldering the coil to the board, place a drop of contact or 
   silicon glue under the coil to prevent mechanical vibration.

4. On the Compound unit, solder two springs (part number G02-0550-04) 
   to the heat sink as shown in figure 1. The springs must be mounted 
   high enough to make firm contact with the top cover when installed.

5. On the PLL unit, solder a spring (part number F10-1206-04) to the 
   TX VCO shield (see figure 2). The spring must make firm contact with 
   the bottom cover when installed.

CAUTION: The next step requires complete disassembly of the front panel 
         and Display unit. This step may be reserved for problem units.


6. On the Display unit, replace Jumper JP3 with a diode (part number 1S1555) 
   as shown in figure 3.

7. Reassemble the transceiver and test the modulation for correct adjustment:

1. Apply a lKHz, 50mV signal to pin 1 of the mic Jack.
2. Turn VR7 on the Compound unit fully CCW .
3. Use a service monitor, linear detector, or deviation meter to measure 
   the TX deviation at the antenna Jack.
4. AdJust VR5 on the compound unit for +/-4.5KHz.
5. Reduce the mic signal to 5mV. AdJust VR7 for +/-3.OKHz.

Time required for this modification is 1 hour or less.