B+ Routing For Vhf/Uhf Transceiver Boards; Figure 1 . B+ Routing For Vhf/Uhf Transceiver Boards - Motorola ASTRO Digital Saber Service Manual

B+ Routing for
VHF/UHF
Transceiver Boards
RX
RF Amp
SB+
U1
Mixer
U2
Q107
R5

Figure 1 . B+ Routing for VHF/UHF Transceiver Boards

4-2
Refer to Figure 1 and your specific schematic diagram.
Raw B+ (7.5V) from the battery (Batt B+) enters the radio on the
transceiver board through a 3-contact spring pin arrangement (J3) as
B+, where it is routed through two ferrite beads on the VHF (E1, E101)
and three ferrite beads on the UHF (E1, E101, E106) to the RF power
amplifier module (U105) and ALC IC (U101, pin 13). Battery B+ is
fused, and then routed through the connector J1, pins 19 and 20 to the
VOCON board (J401, pins 19 and 20). The B+ supply is routed through
the VOCON board to the on/off/volume control knob (S901/R901) on
the control top/PTT flex at jack J901, pin 1. With the mechanical on/
off switch (S901) placed in the "on" position, switched B+ (B+ SENSE)
is routed from the control top flex at connector plug P901, pin 10 and
applied to the VOCON board at connector jack J901, pin 10. This
signal is also fed to a resistive divider R222, R223 on the VOCON board
so that the microcontrol unit (U204) can monitor the battery voltage.
VHF/UHF Transceiver Board
L105
CR109
CR108
L122
L121
T5
RX/TX
5V Regulator
U106
The switched B+ voltage supplies power to circuits on the transceiver
board. The 5-volt regulator (U202), is applied this voltage through
decoupling component C125 to produce a stable 5.0 volt output. Raw
B+ (7.5V), which is connected to the ALC IC (U101), is switched
through the output (CATH1) to another 5-volt regulator (U106).
Regulator U202 supplies those circuits which need to remain on at all
times, such as the reference oscillator (U203), fractional-N-synthesizer
(U204), D/A IC (U102), and the ABACUS IC (U401). The D/A IC
controls dc switching of the transceiver board. The SC1 signal at U102
pin 12 controls transistors Q107, Q111, and the transmit 5 volts (T5).
To/From VOCON Board
SW B+
T5
RF PA Module
U105
ALC U101
VCOB IC
Vcc 5V Regulator
U201
U202
S
Out
Ref Osc ABACUS
Synth
U204 U203 U401
Raw B+
Fuse
UNSW B+
+
Battery
5V
D/A IC IF Amp
U102 Q601
MAEPF-24700-O
7.5V