Kenwood TR-7400A Operating Manual page 13

If your transceiver fails to work, contact the authorized
dealer from which you purchased it for quick, reliable
repair. All adjustable trimmers and coils in your transceiver
were preset at ihe factory and should only be readjusted
by a qualified technician with proper test equipment,
HOW THE TX FINAL TRANSISTORS ARE
PROTECTED
The TX unit final transistor protection provided in the TR-
7400A is done by sampling the reflected power. As the
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SECTION 5. ADDITIONAL INFORMATION
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reflected power is increased (higher SWR) the voltage to the
driver transistors is reduced.
If the transmit signal does not reach an expected distant
point, check the antenna system. That is, whether the anten-
na and coaxial cable is well connected or not. If it is open,
or the SWR is infinite, the transmit signal is on the air,
but the protection circuit operates such that the driver
transistor collector voltage is lowered to decréase the level
of the signal input to the final transistors, which in turn
reduces collector loss, thus protecting the final transistors.
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