Kenwood TK-90 Service Manual page 33

COMPONENTS DESCRIPTION /
Ref. No. Use / Function
Q9 Switching
Q10 Switching
Q11~14 Switching
D1,2 1.8V zener diode
D3~5 Limiter
D6 Limiter
D7 LED
D8~19 LED
3. TX-RX Unit (X57-7210-20)
Ref. No. Use / Function
IC1 Shift register
IC101 Mixer
IC251 Mixer IC
IC361 OP amplifier
IC362 OP amplifier
IC363 A/D
IC421 Shift register
IC422 Analog switch
Operation / Condition
TX indication LED switch
Busy indication LED switch
Dimmer control
Voltage protection
Surge prevention
Voltage protection
TX/Busy indication
LCD backlight
Operation / Condition
Q0: L when BPF4 is selected
Q1: L when BPF5 is selected
Q2: L when BPF6 is selected
Q3: L when BPF3 is selected
Q4: L when BPF1 is selected
Q5: L when BPF7 is selected
Q6: L when BPF8 is selected
Q7: L when BPF2 is selected
Q8: L when FAN1 is selected
Q9: L when FAN2 is selected
Q10: H when ATT is ON
Q11: H when preamplifier is ON
Transmission mixer
TX modulator
Final current protection
Drive current protection
VSWR protection
Electrical volume
Q0: TX boost
Q1: FSK select
Q2: NC
Q3: AM control
Q4: OP filter loss
Q5: AGC slow switch
Q6: AGC off switch
Q7: VGS-1 switch
Q8: KPE-2 switch
Q9: IF filter select signal (Option)
Q10: IF filter select signal (2.4k)
Q11: IF filter select signal (6k)
AGC time constant changeover
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33