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World of Ham Radio 1997
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1997-02-01
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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 # 948
MODEL: TS-440S
SUBJECT: NOTCH FILTER LOW FREQUENCY IMPROVEMENTS
The low frequency attenuation characteristics of the notch
filter can be improved by reducing the input level to the
notch filter chip (IC1). To compensate for the loss of input
level, the amount of negative feedback to the audio
amplifier (IC7) will need to be reduced. This modification
is already incorporated in all models beginning with serial
number 704XXXX.
REQUIRED PARTS:
120K OHM, 1/6 WATT RESISTOR ........ RD14CB2C124J
390 OHM, 1/6 WATT RESISTOR ........ RD14CB2C391J
1. Disconnect the power supply and antenna.
2. Using a #2 Phillips screw driver, remove the 9 screws
from the top cover. Remove the top cover from the
transceiver and unplug the speaker wire.
3. Locate resistors R86 and R229 on the component side of
the IF board (Figure 1).
4. Using a #1 Phillips screw driver, remove the 7 screws
that secure the IF unit to the chassis of the
transceiver.
5. Pull the board up and rotate it towards the front of the
transceiver to expose the foil side of the board.
6. Desolder and remove both resistors from the board.
7. Install and solder a 102K ohm resistor in place of R86.
8. Install and solder a 390 ohm resistor in place of R229.
9. Assemble the transceiver by reversing steps 1 - 5.
Time required for this modification is 0.5 hrs or less.