Power On/Off; Miscellaneous Functions; W4, W5, And W7 Control Heads; Power Switch/Ignition - Motorola ASTRO W3 Service Manual

3-4

3.1.10 Power On/Off

The HHCH has the ability to turn a host radio on or off by activating S6, which then places a
momentary logic low on the Mic Hi line. This is detected by appropriate circuitry in the host radio,
which then reverses the power on/off state of the radio. Since the microphone power is supplied by a
switched Opt B+ line from the radio, the microphone power on/off state follows that of the radio.

3.1.11 Miscellaneous Functions

If TP1 contacts are momentarily shorted or certain key combinations are pressed simultaneously, the
HHCH is placed in its test mode to carry out various diagnostic checks.
Transient protection diodes D24, D25, D37, D38, and D39 provide electrostatic transient protection
for sensitive components within the HHCH by preventing voltages from going outside the specified
ranges for these components.
3.2

W4, W5, and W7 Control Heads

The following pages describe the operational theory of the components of the W4, W5, and W7
control heads. Refer to
A+/IGN
13.8V
1 JU1 2
A+
JU2
1 2
IGNITION
3.2.1

Power Switch/Ignition

For dash-mounted radios, a pushbutton On/Off switch (S1) (or rotary knob on the W4 control head)
on the front panel controls power to the radio and accessories. In addition to this switch, you can wire
the vehicle's ignition and add or remove control-head jumpers to further control radio operation.
Type
1 RECEIVE and TRANSMIT enabled
via control head ON/OFF switch
(ignition has no effect).
2 RECEIVE and TRANSMIT enabled
only when ignition switch is ON.
September 26, 2003
Figure 3-1 for the control-head components.
(U3, Q50, T60)
37 VDC
VOLTAGE
CONVERTER
CIRCUITRY
+5 VDC
U45
5 VOLT
REGULATOR

Figure 3-1. Astro Spectra Control Head Block Diagram

Table 3-2. Types of Operations

How it Operates
Theory of Operation: W4, W5, and W7 Control Heads
U101
34 VDC
VF DRIVER
IC FLUORESCENT
2.5 VAC
VIP OUTPUTS
COMPUTER
INTERFACE
SERIAL DATA BUS
VIP INPUTS
WATCHDOG
IGNITION SENSE
PTT SENSE
HUB SENSE
Control Head
Jumper/Status
JU1OUT; JU2/IN Connect ignition cable to
"Battery Hot" at fuse block.
JU1/OUT; JU2/IN Connect ignition cable to
"Ignition" at fuse block.
U102
VACUUM BACKLIGHT
LEDS
DISPLAY
U1
1
MICRO-
Y1
4.0 MHz
2
U4
AND
TIMER IC
Ignition Wiring
6881096C77-O