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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 # 1056
MODEL: TM-732A
SUBJECT: APC Circuit Improvement
Symptom:
Failures of APC circuit transistor Q232 can occasionally be attributed to
the gain dispersion characteristics of the VHF power module. Some of these
devices allow normal transmit power output even with reduced "DB" terminal
voltages. If the unit is then operated for extended transmit key down
periods Q232 can overheat and fail.
Corrective Action:
1. Measure the transmit power output and the "DB" terminal voltage at a
dial frequency of 145.020 MHz.
2. Add the 1 dB circuit if the transmitter power is 60 W or greater and
the "DB" terminal voltage is 10 vdc or less.
3. After adding the attenuator, re-adjust the transmitter output power for
50 W and check the "DB" voltage. The "DB" voltage should now fall between
10 and 11 vdc. lf it does not adjust the values for R98, R100, and R99 until
this voltage range is obtained.
Parts Required:
Description Part No. Circuit Description
820 ohm chip resistor RK73FB2A821J R98, R100
470 ohm chip resistor RK73FB2A471J R98, R100
270 ohm chip resistor RK73FB2A271J R98, R 100
5.6 ohm chip resistor RK73FB2A5R6J R99
10 ohm chip resistor RK73FB2A100J R99
18 ohm chip resistor RK73FB2A180J R99
*Note: Quantities vary depending upon level of attenuation required to meet
requirements of step 3.
Pad Attenuation R98, R100 R99
1 dB 820 ohms 5.6 ohms
2 dB 470 ohms 10 ohms
3 dB 270 ohms 18 ohms
IC-10 <--------R99--------> VHF POWER MODULE INPUT
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R98 R100
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GND GND
TX-RX UNIT (X57-4000-02 A/4)
Time required for this modification is 60 minutes or less.
Service code A:84 B:X57-4000 C:R99 D:91