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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 # 991
MODEL: TS-950S
SUBJECT: Rear Panel Coolinfs Fan
The 50 watt power down circuit will begin to operate if the cooling fan on
the rear panel fails to operate after 15 minutes of continuous transmission
in order to protect the final amplifier circuit. Failure of the fan will
prevent the power down circuit from returning transmit power to normal
levels since the transformer temperature remains high. This trouble can
sometimes be traced to a pinched/burnt wire near resistor R17 of the AVR
unit (X43-3070-01).
Cause:
If the red wire attached to connector CN2 of the AVR unit is pinched
between the chassis and ground the insulation might be damaged and allow
this line to short to the chassis. This wire supplies 15 vdc to the fan
motor thru resistor R17. Excessive current is drawn thru R17 under this
circumstance, approximately 1.5A rather than the normal 0.5A. This can
cause the resistor to become red hot and damage the surrounding circuit
board, since R17 is a metal oxide film resistor.
Corrective action:
R17 should be replaced with a ceramic resistor if this symptom is encountered.
Replacing the metal oxide film resistor with a ceramic resistor will prevent
damage to the circuit board should the red lead become shorted.
Parts Required:
10 ohm 2 Watt Ceramic resistor R92-1285-05
Procedure:
Change R17 to R92-1285-05 (Ceramic Resistor)