B+ Routing For 800Mhz Transceiver Boards - Motorola ASTRO XTS 3000 R Detailed Service Manual

B+ Routing for
800MHz
Transceiver Boards
Rx
CR104
L101
CR102
Mixer
RF Amp
U202 U205
Refer to Figure 3 and the appropriate schematic diagram.
Raw B+ (7.5V) from the battery (Batt B+) enters the radio on the
transceiver board through a 3-contact connector (J3). From J3 it is
routed through four ferrite beads (E1, E2, E3, E4) and applied to the RF
power amplifier (U502) and the ALC IC (U504). Battery B+ is fused and
then routed to the controller board, where it enters on connector J1,
pins 15 and 20. On secure radios, Raw B+ is also routed to the
encryption board so that it can perform key management and other
functions independent of SW B+.
800MHz Transceiver Board
ALC
U504
Q503
Synth
U302
Figure 3 B+ Routing for 800MHz Transceiver Boards
The SW B+ is applied to the 5V regulator (U305) to produce a stable
5.0 volt output. Regulator U305 supplies those circuits which need to
remain on at all times, such as the reference oscillator (U304),
fractional-N synthesizer (U302), D/A IC (U503), and the ABACUS IC
(U401). The D/A IC controls dc switching of the transceiver board. The
SCI signal at U503, pin B4 controls Q503 and transmit 5 volts (T5). The
SC3 signal at U503, pin C4 controls the RX 5V switch in Q503 and the
receive 5 volts (R5). During the receive mode, switch Q503 supplies
regulated 5volts (R5) to the receiver front end.
To/From Controller Board
SW B+
UNSW B+
RF PA
VCO
Module
U307
U502
5V Regulator
VCOB IC
U305
U303
Ref Osc ABACUS
D/A IC
U304 U401
Raw B+
Fuse
5V
IF Amp
U503
Q601
MAEPF-25995-O
+
Battery
7.5V
3-3