Kenwood TM-221A Service Manual page 11

TM-221A/E/ES
DESCRIPTION OF ELEMENTS
FINAL UNIT (X45-1330-03) : TM-221E, (X45-1360-02) : TM-221A/ES
| Element | Function Description
Boosts power to the required level. M57747 in TM-221E, M57726 in TM-221A/ES.
Protection against reverse power connection
D2,D3 Transmit/receive select ON during transmit. .
High-frequency output voltage level detect Detects high-frequency output level and controls output in the APC circuit.
Reflected power detector Adjustable with VR1.
CONTROL UNIT (X53-3040-XX)
Element Function Description
Ici 6V AVR
IC2 Reset IC Outputs Reset signal and detects iow voltage.
{C3 Microprocessor Controls frequencies and general set functions.
Converts digital data from IC3 (P40 to P43, P50 to P53) to an analog tone
frequency.
Q1 Squelch switching Switches squelch on/off when remote controller is connected.
IC4 Tone DAC
Q2 Switching Controls the microprocessor's backup detect input.
Di Reverse current protection Protects against external voltage applied to pin 5 of the microprocessor.
Microprocessor protection Protects against static surge.
D2(2/2) | Voltage drop a
D3(1/2) | Reverse current protection Prevents current from flowing to the backup battery.
D3(2/2) Reverse current protection Prevents backup battery current from flowing to inappropriate circuits.
D4 Microprocessor protection Protects against static surge.
TX-RX UNIT (X57-3060-XX)
{C1 8V AVR
IC2 PLL Pulse-swallow type phase-locked loop.
Shift register Controls alert (T,W), band switching, and electronic volume functions.
AF amplifier Speaker output,
Qi High-frequency amplifier Operates in receive mode (144MHz).
Converts the 2 meter-band received frequency into the 10.695MHz (K,M)
Q2 First mixer 10.7MHz (T,W).
Q3 High-frequency amplifier First intermediate frequency amplifies.
as AP anaalig Operates when cTcss is ON (KM), during priority reception when alert is ON
(T,W), when SOS is high, and jn transmit mode.
Q5 8R switching ON in receive mode.
Q6 8T switching ON in transmit mode.
8T switching control ON in transmit mode.
Q8 8R switching control ON in receive mode.
Qg Constant-voltage control 5V power supply for PLL.
Q10 Buffer amplifier Buffer amplifier for Q12, which amplifies the 10.24MHz crystal oscillator (K,M).
O11 High-frequency amplifier Amplifies 12.8MHz to the level required for the PLL (T,W).
Q12 High-frequency amplifier Amplifies 10.24MHz to the level required for the PLL (K,M).
Q13,014 | PLL low-pass filter L
Q15 PLL unlock control ON when the PLL is locked.
High-frequency amplifier Amplifies the VCO output to the level required for the PLL.
High-frequency amplifier Amplifies the VCO output to the level required for input to the 1st IF mixer (Q2).
isvertingeaipifiee Inverts the output from the BS port of the shift register (HI1/LO >
LO (OV)/HI (8V).
Transmit driver {power amplifier) Amplifies to the level required for input to the final unit power module.
+B (DB) AVR of Q19 Operates in transmit mode.
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