Icom IC-F50, IC-F51 service manual 4 D/A Converter IC Main Unit IC6, Expander IC Main Unit IC12

4-6-3 EXPANDER IC (FRONT UNIT; IC410)

Pin	Port	Description
number	name
4	LEDR	Outputs RX LED control signal.
		Low: Lights ON.
5	LEDT	Outputs TX LED control signal.
		Low: Lights ON.
6	LIGT	Outputs back light LED control signal.
		Low: Back light is ON.
		Outputs audio control signal.
7	AFON	Low: Outputs audio signals from
		speaker.
		• Outputs CTCSS/DTCS switching sig-
		nal when transmitting.
		High: Selected DTCS.
		• Outputs Min. VR switching signal
11	DUSE	when receiving.
		Low: Select Min VR.
		NOTE: Audio signals are prior to
		transmitting.
		Outputs microphone select signal.
12	MCON	High: While the internal microphone
		is used.
13	CSFT	Outputs shift signal for reference oscil-
		lator’s frequency.
		Outputs the internal speaker control
14	SPON	signal.
		High: The internal speaker is select-
		ed.

4-6-4 D/A CONVERTER IC (MAIN UNIT; IC6)

Pin	Port	Description
number	name
		Outputs the modulation balance level
11	BAL	control signal. The signal is applied to
		the buffer amplifier (IC16, pin 2).
		• Outputs the bandpass filter tuning
		signal. The output signal is applied to
14	T2	the bandpass filters (D9, D10).
		• Outputs the TX power control signal.
		The output signal is applied to the
		APC amplifier (IC2, pin 1).
		Outputs the bandpass filter tuning sig-
15	T1	nal. The output signal is applied to the
		bandpass filters (D4, D8).
		Outputs the PLL lock voltage control
22	LVA	signal. The output signal is applied to
		the buffer amplifier (IC16, pin 5).
		Outputs the reference oscillator cor-
23	REF	recting voltage. The voltage is applied
		to the buffer amplifier (IC16, pin 3).

4-6-5 EXPANDER IC (MAIN UNIT; IC12)

Pin	Port		Description
number	name
		Outputs the R5 regulator (Q22) control
4	R5C	signal.
		Low: While receiving.
		Outputs the T5 regulator (Q21) control
5	T5C	signal.
		Low: While transmitting.
		Outputs the S5 regulator (Q23–Q25)
6	LIGT	control signal.
		Low: While the S5 regulator outputs
		5 V voltage.
		Outputs audio control signal.
7	AFON	Low: Outputs audio signals from
		speaker.
		Outputs the analog switch (IC13, pins
		5, 6) control signal to control the
		scrambler unit.
11	MUT2	High: While the scrambler function is
		ON.
		Low: While the microphone mute or
		AF mute is ON.
		Outputs the analog switch (IC13, pins
		12, 13) control signal to control the
		scrambler unit.
12	MUT1	High: While the scrambler function is
		ON.
		Low: While the microphone mute or
		AF mute is ON.
		Outputs	the	FM/PM	modulation
13	PMFM	switching signal to the FM/PM switch
		(IC11, pin 5).
		High: PM is selected.
		Outputs the transmitting mute switch
14	TMUT	control	signal	to the	mute switch
		(D25).
		High: While muting.

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