28
TK-885
PA Switch
If the optional KAP-1 is used, the PA (Public Address) func-
tion becomes available. In this case, the signal flow changes
as follows;
“PA2”
Q507
SW.A
SW.B
SW.D
Public address
L
L
L
H
H
OFF
H
H
H
L
L
ON
Fig. 17 Power supply circuit /
Fig. 16 PA switch /
Power Supply Circuit
When the POWER switch on the control unit is pressed,
the PSW signal goes low. This signal is inverted by Q26 and
sent to a flip-flop IC (IC15). This IC outputs a control signal
when the PSW goes low. When the power turns on, pin 1 of
IC15 outputs a low signal and Q30 turns on. The base of Q28
goes high, Q28 turns on, SB SW (Q27) turns on and power
(SB) is supplied to the set.
This circuit has an over-voltage protection circuit. If a DC
voltage of 20 V or higher is applied to the power cable, D34
turns on and a voltage is applied to the base of Q31. This
voltage turns Q31 on and turns Q28 and SBSW off. This
circuit has a TIMED POWER OFF (TOF) function which can
be programmed by software.
It is controlled through pin 6 of IC7. When the TOF line
goes high, Q22 turns on and then Q25 turns on. Pin 6 of IC15
goes high, then pin 1 goes high to turn Q27 off.
SW.D
SW.B
SW.A
TXOUT
MSKGS
RXIN
IC504
Audio
processor
RXOUT
IC506
Analog
SW
MO
47K
Q507
5C
PA2
Q27
SW
Q28
SW
Q30
SW
Q25
SW
Q22
SW
Q26
INV.
IC15
F.F.
Q31
SW
D34
SW
R152
R151
IGN
SB
+B
PSW
TOF
IC7
6pin
CIRCUIT DESCRIPTION /
Содержание TK-885
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