Kenwood TS-60S Service Manual page 13

CIRCUIT DESCRIPTION
3. Protection circuit
When the reflected wave voltage (VSR) detected by
the filter unit rises, Q6 (2SC2714(Y)) in IC11 turns on t o
reduce the voltage of the ALC time constant line. The
drive is decreased and the power is reduced t o protect
the final transistor.
4.
Temperature protection
If the final heat sink temperature rises, 0 8 in the
final unit turns on and the fan starts running at low
speed in both transmit and receive modes. If the final
heat sink temperature rises further, Q9 turns on, and
the fan rotates at medium speed in both transmit and
receive modes. If the temperature rises further still,
the fan rotates at high speed in transmit mode, and at
7
medium speed in receive mode t o reduce the fan
noise.
If the temperature continues t o rise, the tempera-
ture detection port of the microcomputer (IC1 in the
digital unit) is made high t o reduce the RF output forci-
bly. If the fan fails or does not rotate because some-
thing is stopping it, the RF output is forcibly reduced in
the same way.
2. Reset circuit
IC4 (M62003FP) monitors Vcc applied to the micro-
computer. If the voltage falls below 2.15V, the IC out-
puts a reset signal (low) to the microcomputer, and the
CPU initializes all internal data (including memory chan-
nel data). The reset signal is not output when the
power is turned on or off or 14V is turned on or off. It is
output when the battery voltage level goes low and
14V is turned on or off.
C35 generates the signal width (td) required to reset
the microcomputer. (Fig. 12)
Digital Control Circuit
4.35~
The TS-GOS digital control circuit comprises a 16-bit
2,15V
microcomputer (M37702M4A-FP), a reset IC
(M62003FP), an EEPROM (NM93C66LEM8 or
AT93C66-10S12.7), a latch (TC74HC573AFL and a de-
coder (TC74HC238AF). The latch and decoder are
1
'
1
used to expand the output ports. The decoder outputs
an enable signal pulse.
-
1. Power button
With this transceive, the power is turned on and off
RESET RESET
by the microcomputer. When the power bunon is
pressed, the microcomputer detects it and energizes,
Fig. 12 Reset circuit
the power relay t o supply 14V t o the transceiver.
When the power button is pressed to turn the trans-
ceiver off, the microcomputer checks it a little longer
than when turning the power on, and deenergizes the
power relay.