EFJohnson 764X, 761X service manual Vhf Ic Pin Descriptions, Line, Port

VHF (7610) CIRCUIT DESCRIPTION

The phase detector determines the phase differ- ence between these signals and then produces output pulses on pin 8 which are filtered by the loop filter.

This filter consists of R43-R45, C60, and C61. The output of this filter is the DC control voltage applied to the VCO. The phase detector increases or decreases this control voltage to change the VCO frequency.

5.3.2 VCO CIRCUIT

The VCO signal is amplified by buffer amplifiers Q6 and Q4 and is then applied to T/R switch D5 and D6. The VCO receive injection signal is applied to first mixer Q13 via bandpass filter L23, L24, and C116-C118. Likewise, the VCO transmit signal is applied to driver Q1 via buffer amplifiers Q2 and Q3. Part of the Q6 output signal is fed back to PLL IC2 as described in the preceding section.

5.4 VHF IC PIN DESCRIPTIONS

5.4.1 VHF POWER SUPPLY

Line	Description
VCC	Unswitched input voltage to the transceiver.
HV	VCC supply voltage switched by Q25 and Q26.
	When the [POWER] switch is pressed, the CPU
	outputs the “PWON” control signal to this circuit
	to turn the HV supply on.
CPU5V	Common 5V supply for the CPU produced from
	the VCC supply by CPU5V regulator IC9. The
	circuit outputs this voltage regardless of the
	transceiver on-off condition.
8V	Common 8V supply produced from the HV
	supply by 8V regulator Q36.
5V	Common 5V supply produced from the VCC
	supply by 5V regulator Q29/Q30.
R5	Receive 5V supply produced by R5 regulator
	Q27 using the “T5C” signal from I/O expander
	IC IC11.
T5	Transmit 5V supply controlled by T5 regulator
	Q28 using the “T5C” signal from I/O expander
	IC11.

5.4.2 VHF CPU IC1 PORT ALLOCATION

Pin	Port	Description
No.	Name
1	VIN	Input port for overvoltage detection from
		the vehicle power source.
12	SCK	Outputs clock signal to EEPROM IC3,
		PLL IC2 (main unit) and expanders IC5,
		IC11 (main unit), etc.
13	SI	Input port for the data signal from
		EEPROM IC3, etc.
14	SO	Outputs data signal to EEPROM IC3, PLL
		IC2 (main unit) and expanders IC5, IC11
		(main unit).
16	CLIN	Input port for cloning signal.
17	CLOUT	Output port for cloning signal.
18	POSW	Input for the POWER switch. Low =
		POWER switch pushed.
19	NOIS	NOIS signal input port from the FM IF
		IC3 (main unit) for noise squelch
		operation.
26	PTT	Input port for the PTT switch. Low = PTT
		switch pushed.
32	RFATT	Outputs RF attenuator control signal to the
		attenuator switch (Q35 on main unit).
		Low = Attenuator function on.
36	UNLK	Input port for PLL unlock signal from the
		PLL IC2 (main unit). High = unlock.
37	PWON	Outputs control signal for the power
		switching circuit (Q25 on main unit) and
		5V regulator Q29, Q30 (main unit).
38	DIM	Outputs control signal for LCD backlight.
		Low = LCD backlight on.
39	EXTPTT	Input port for the PTT switch from exter-
		nal connector J3 (main unit). Low = Exter-
		nal PTT switch on.
40	DIM	Input port for the LCD backlight control
		signal from external connector J3 (main
		unit). Low = External dimmer switch on.
41	PLST	Outputs strobe signals for PLL IC2 (main
		unit).
42	DAST	Outputs strobe signals for level controller
		IC5 (main unit).
43	EXST	Outputs strobe signals for the I/O
		expander IC11 (main unit).
45,	KS1,	Output ports for the key matrix.
46	KS2
47-	KR3-	Input ports for the key matrix.
50	KR10

	November 1998
5A-5	Part No. 001-7600-001