Pll Data Output; Horn Control; Power Supply Circuit - Kenwood TK-940 Service Manual

CIRCUIT DESCRIPTION
6-4. PLL data output
PLL data is output fronl DATA (pin 61
),
EIUABLE (pin
8c
HOR
591, and CLOCK ( p ~ n
60)
of the CPU (IC2091. The sig-
nas are input t o the PLL IC ( I C l i when the channel is
0 1 3
changed or when transmission is changed to reception
and vice versa.
6-5. Horn control
014
The horn switch, consisting of Q13, 014, and Q29,
controls the horn relay. It is supplied by the dealer t o
Q29-
provide the external horn alert function.
R2 R16
r
IGN
0 2 9 disables horn alert, turning on when its base is
high, to inh~bit the function. Normally, the output from
lClO is low, and 0 1 3 is off; the baseof 0 1 4 is about O V
and 0 1 4 is off. When horn alert is enabled, the output
from lClO goes high and Q13 turns on. The base
current flows through RE1 t o Q14 to turn Q14 on. Q14
Fig. 8 Horn control circuit
can sink a minimum of 800mA.
6-6. Power supply circuit
D8 protects 1C1 against overvoltage. Each time a
pulse comes from the PSW terminal, the IC1 output is
reversed. The reversed output signal passes through
0 1 and Q3 and drives 0 4 . A voltage must be applied to
the IGN terminal.
If 24V is supplied t o the transceiver by mistake, Q2
turns on, and 0 3 and 0 4 are forced o f f , so t h e
transceiver does not turn on.
If the SB terminal of the modular jack to which the
microphone is connected is shorted or an overcurrent
flows, R122 and R123 convert the current to a voltage
and 0 3 0 turns on. Its output drives 0 2 8 and turns Q27
on, and the IC1 output foes high. This turns the
transceiver off. If the terminal is no longer shorted, the
transceiver can be turned on by pressing the power
key. R125andC161 are used to prevent malfunction-
ing w h e n a device w i t h a large surge current is
connected.
Fig. 9 Power supply circuit
BO
1
T
-
SW
-
SB
D8
LO
R122, R123
AVR
LT
4)
vAvA,
=
SB
I
03 030
a+
IC1
(To rectangular
receptacle)
Q27 0 1 SW
-
SW
-
-
SW DEF SW
PSW