Alinco DR-235, Service Manual

Page: 6 / 40

4. S (Signal) Meter Circuit
The DC potential of pin 12 of iC108 is input to pin 1 of the CPU (IC1),
converted from an analog to a digital signal, and displayed as the S-meter
signal on the LCD.
5. DTMF Encoder
The CPU (IC1) is equipped with an internal DTMF encoder. The DTMF
signal is output from pin 10, through R35, R34 and R261 (for level
adjustment), and then through the microphone amplifier (IC114:D), and is
sent to the varicap of the VCO for modulation. At the same time, the
monitoring tone passes through the AF circuit and is output form the
speaker.
6. Tone Encoder
The CPU (IC1) is equipped with an internal tone encoder. The tone signal
(67.0 to 250.3 Hz) is output from pin 9 of the CPU to the varicap (D120) of
the VCO for modulation.
7. DCS Encoder
The CPU (IC1) is equipped with an internal DCS code encoder. The
code (023 to 754) is output from pin 9 of the CPU to the PLL reference
oscillator. When DCS is ON, DCS MUTE circuit (Q126-ON, Q133-ON,
Q132-OFF) works. The modulation activates in X102 side only.
8. CTCSS, DCS Decoder
The voice band of the AF output signal from pin 3 of IC120:A is cut by
sharp active fitter IC104:A and D (VCVS) and amplified, then ied to pin 4
of CPU. The input signal is compared with the programmed tone
frequency code in the CPU. The squelch will open when they match.
During DCS, Q108 is ON, C419 is working and cut off frequency is
lowered.
5 ) P o w e r S u p p l y C i r c u i t
When power supply is ON, there is a "L" signal being inputted to pin 39 (PSW) of CPU which enables the CPU to
work. Then, "H" signal is outputted from the pin 41 (C5C) of CPU and drives ON the power supply switch control
Q8 and Q7 which turns the 5VS ON.5VS turns ON the PLL IC116, main power supply switch Q127 and Q122, AF
POWER IC117 and the 8 V of AVR (IC115).During reception, pin 29 (R5) of CPU outputs "H" level, Q124 is ON,
and the reception circuits supplied by 8 V.While during transmission, pin 28 (T5) of CPU outputs "L" level which is
reverse by Q11 so that the output in Q128 will be "H" level, Q123 is ON, and the transmission circuit is supplied by
8 V.Or, in the case when the condition of PLL is UNLOCK, "L" level is outputted from pin 14 of IC116, UNLOCK
switch Q148 is OFF,Q129is ON, transmission switch Q128 is OFF which makes the transmission to stop.
1. ACC External Power Supply Terminal
When optional power supply cord DEC-37 etc. is connected to the
external power supply terminal JK101, with ACC power supply ON, switch
Q101 will turn ON, 5 V of AVR IC101 pin 2 (STB) becomes "L" which
makes C5V to turn ON. With this, it can turn the power supply of the radio
ON.
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