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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 # 942
MODEL: ALL
SUBJECT: SERVICE MANUAL TX LEVEL DIAGRAMS 10/30/88
INTRODUCTION
Kenwood service manual transmit level diagrams provide typical RF levels
found in working transceivers. This information provides a fast method
of locating a faulty circuit in a transmitter chain. To use the level
diagrams, an AF VTVM, RF VTVM, and 50 ohm resistive load are required.
In addition, since many units are tested with the drive output terminated
into the load, a coax cable must be fabricated. A sample cable is shown
below.
HOW THE TX LEVEL DIAGRAM IS DEVELOPED
The transmit level diagrams are developed in a similar manner as the
receive diagrams. Basically, a working transceiver is tuned for a specified
output power at center frequency. The mic audio circuit is measured with
an AF VTVM and the RF circuit is measured with an RF VTVM. The results
are listed on the diagram as typical levels for a working transceiver.
The exact setup used to make a diagram varies with the model. The setup
details are listed in footnotes on the diagram. No matter what procedure
is used, the end result is a list of typical levels for a working
transceiver.
For the most part, variations in setup include what mode is used, if audio
is applied to the mic input, and what reference is used for power output.
Additionally, many units have the drive signal connected directly to a
50 ohm load. This requires a fabricated coax cable that can be inserted
into the drive socket and attached to a load. A coax cable with a terminal
that fits the drive socket is available in the Kenwood Parts Department.
SB-905 lists the part numbers of coax cables that are available in
several lengths and style. Once a cable is obtained, a connector that
matches your 50 ohm load can be soldered to the cable.
USING THE TX LEVEL DIAGRAMS
As mentioned above, certain units are terminated at the drive output.
This procedure can be used in troubleshooting to determine if normal
drive power is available. Simply connect the fabricated coax cable to
the drive terminal and the 50 ohm load. If the load receives full drive
power as indicated on the level diagram, the trouble spot is in the Final
or LPF unit. In this case, reconnect the Final unit and continue
checking towards the antenna terminal. If low drive is measured, continue
measuring towards the mic input until a faulty circuit is found.
NOTE
Once a faulty circuit is isolated, DC measurements must be made to
determine if normal supply voltage is present.