Kenwood TS-440S Serivce Manual page 13

TS-440 S
CIRCUIT DESCRIPTIO N
Vs F is compared with voltage from IC8 pin 6 (5 .5 V) .
When SWR increases, VSF
lowers and the voltage leve l
of IC8 pin 8 rises . At IC7 pin 3, a triangular wave is moni -
tored . The triangular wave is compared with the wav e
from IC8 pin 8 and output . The triangular wave is con-
verted to a square wave by IC10 and sent to switch Q 3
and Q4 . This voltage is used as the SWR control voltage .
Output voltage from IC8 pin 2 consists of the voltage com -
pared with VsR/Vs F and + 5 DC voltage . It is distribute d
to IC4 the level shift/meter amplifier to move the needl e
in the SWR meter and IC5 the V-I convertor to control th e
AT440 .
VR14 is used to adjust the SWR meter ZERO point .
VR 13 is for SWR meter adjustmen t
3) FULL/SEMI BREAK-IN and VOX circuits
RL TXB RX B
MICROPROCESSOR
STAND-B Y
CIRCUIT
CONTRO L
POWER SUPPLY
CONTRO L
CIRCUIT
KEYIN G
CIRCUI T
VO X
CIRCUIT
Fig . 9-1 FULL/SEMI BREAK-IN block diagra m
When the standby switch, the key, or the VOX switchin g
transistor are activated, a ground is applied to the input pi n
of the control circuit, which causes a standby signal to b e
fed to the microprocessor to determine if a valid transmit con -
dition has been met . When that condition has been met, th e
KEYIN G
STAND-B Y
VOX
standby circuit in the IF unit will be turned on .
A keying signal is generated by the control circuit, wheneve r
the key is depressed, to control the keying circuits in the I F
unit . This keying signal is also used as the transmit/receiv e
signal during break-in operations .
o KEYING (FULL )
o CONTROL( FULL )
o KEYING(SEMI )
0
CONTROL(SEMI )
Fig . 9-2 FULL/SEMI BREAK-IN timing chart
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