Kenwood TH-22A Service Manual

TH-22A/AT/E
22
DESCRIPTION OF COMPONENTS
TX-RX unit (X57-437X-XX)
0-11: K,P 0-21: M1 0-22: M2,M3,M4 0-23: M5 0-71: X 2-71: E1,£3,£4,£9,T 2-72: E2
Ref. No. Use/Function Operation/Condition/Compatibility
IC1 PLL IC
IC2 DC-DC converter About twice the input voltage (3.5 V) is output.
IC3 Transmission power amplifier
IC4 FM IC Second mixer, quadrature detector, AF output, noise amplifier output, S-
meter output
IC201 DTMF receiver
IC202 EEPROM
1C203 3.5V AVR
\C204 APC comparator
IC205 Voltage detection
IC206 Microprocesser
{C207 Microphone amplifier Limiter amplifier, active low-pass filter
1C208 AF power amplifier
IC209 Reset circuit comparator
Q1 Ripple filter
Q2 RF amplifier PLL IC 8-pin IN (fin amplifier)
Q3, 04 Charge pump
Q5 DC buffer amplifier
Q6 RF power amplifier First stage of driver
Q7 RF power amplifier Second stage of driver
a8 First mixer 144MHz band — 45.05MHz band
Q9 RF amplifier 144MHz first stage
Qi0 Noise amplifier
Qli \F amplifier MCF post amplifier
Qt 2 Active high-pass filter
Q13 Mute switch Mute switch; "H”: Receive audio signal On
Q14 Constant-current circuit
Q15 Power module protection switch
Q16 Current limit circuit
Q201 Transmission power changeover switch See the circuit description of the APC circuit and transmission
changeover circuit.
Q202 DC SW APC circuit reference voltage equals SB voltage when EL is On.
Q203 APC voltage control circuit
Q205 Transmission power changeover switch See the circuit description of the APC circuit and transmission
changeover circuit.
Q206 Constant-current circuit
Q207 APC circuit power supply switch
Q208 3M SW 3M SW; “L”: ON
Q209 Mute switch Mute switch, "H": Transmission audio signal Off
Q210 AVR AF amplifier power supply
Q211 Error amplifier Q13 bias conirol
Q212 AF amplifier power supply switch AF amplifier power supply switch, “L”: On
Q218 AVR 3T
Q214 AVR 3C

Kenwood TH-22A Specifications

General

Brand	Kenwood
Model	TH-22A
Category	Transceiver
Language	English