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World of Ham Radio 1997
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WOHR97_AmSoft_(1997-02-01).iso
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asb1060.txt
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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 # 1060
MODEL: TM-733A
SUBJECT: PL Tone Distortion
Symptom: Transmitted PL Tones at the receiving station have a relatively
high level of distortion. This is easily seen when the incoming signal
is viewed on an oscilloscope.
Countermeasure:
Change the value of the "Pull-up" resistors in the PL tone encoder circuit
as shown in the accompanying chart. This reduces the distortion from
around 9% to approximately 4%.
Parts Required:
Qty Description Old Kenwood Part No. New Kenwoood Part No.
1 R542 (from 1.8K to 2.7K) RK73FB2A182J RK73FB2A272J
1 R543 (from 1.8K to 3.3K) RK73FB2A182J RK73FB2A332J
1 R544 (from 1.8K to 4.7K) RK73FB2A182J RK73FB2A472J
1 R545 (from 1.8K to 6.8K) RK73FB2A182J RK73FB2A682J
1 R546 (from 1.8K to 1OK) RK73FB2A182J RK73FB2A103J
1 R547 (from 1.8K to 1OK) RK73FB2A182J RK73FB2A103J
1 R548 (from 1.8K to 1OK) RK73FB2A182J RK73FB2A103J
Procedure:
1. Disconnect the power cable, microphone and antenna's, etc.
2. Detach the front panel and set it aside.
3. Remove the top and bottom covers.
4. Remove the speaker and speaker mounting bracket
5. Disengage the plastic front panel from the main chassis.
6. Carefully disconnect the two ribbon cables from the TX/RX unit C/4.
7. Remove the two Phillips head screws that secure the TX/RX unit to the
chassis.
8. Turn the circuit board over and replace the resistors using the parts
list above.
9. Reverse steps 1-7 for reassembly.
These components are located on the foil side of TX-RX Unit (X57-4360-00)
near IC402.
Caution: This modification requires advanced surface mount soldering
equipment that is rated for CMOS circuits. It also requires familiarity
with advanced surface mount soldering techniques. If you do not have the
proper equipment or knowledge do not attempt this modification yourself.
Seek qualified assistance from your closest Kenwood Service Center
(Long Beach, CA, or Virginia Beach, VA).
Time required for this modification is 60 minutes or less.
Service code A:06 B:X57-4360 C:R542 D:91