Service manual

CIRCUIT DESCRIPTION
6-13
Month 2000
Part No. 001-2004-601
6.4.1 POWER CONNECTOR
The power supply is connected to the RF Inter-
face Board when the RF module is inserted into the
repeater cabinet (see Figure
10-5). The jack portion of
the connection is on the RF Interface Board, the plug
portion is attached to the station cabinet.
P101/P102 +26.5V DC - Supply voltage to PA.
+26V ±1%, 20A at 110W.
P103 +15V DC - Supply voltage to Exciter, Receiver
and Power Control. 15V ±1%, 5.5A max.
P104/P105 GROUND - Ground return for the RF as-
sembly.
6.4.2 SIGNAL CONNECTOR (J101)
This is the signal interface connector (36 pin) that
connects the RFIB to the backplane connector J2 (34
pin) through cable assembly A8.
Pin 1 GROUND
Pin 1 carries ground current between the RF
Interface board and Backplane board.
Pin 2 PC STR
Pin 2 is the power Control Strobe. This is nor-
mally low until after the power control data is shifted
into the power control register. Then the strobe line
goes high and back to low. The clock or data lines
cannot be changed until after the strobe is set.
Pin 3 HS CS EX
Pin 3 is not used at this time.
Pin 4 GROUND
Pin 4 carries ground current between the RF
Interface board and Backplane board.
Pins 5-6 UNUSED
Pin 7 RX WBAND
The wide band audio is from the receive audio
demodulator U202 and goes to the MAC in the Con
-
troller card cage. The typical amplitude is
387 mV RMS (-6 dBm) and 2V DC with Standard
TIA Test Modulation into the receiver. Little wave
shaping is done on the receiver board other than a
31 kHz RC LPF which strips off the 450 kHz IF.
Buffering is done with an op-amp.
Pin 8 RF DATA A
Data A (U105, pin 11) is the least significant bit
(LSB) in the 3 multiplex chips located on the RFIB.
This pin is a CMOS input from the Controller requir
-
ing a logic high for activation.
Pin 9 RF DATA C
Data C (U105, pin 9) is the most significant bit
(MSB) in the 3 multiplex chips located on the RFIB.
This pin is a CMOS input from the Controller requir
-
ing a logic high for activation.
Pin 10 RF MUX2 INH
The Multiplexer-2 Inhibit (U106, pin 6) is a
CMOS input from the Controller that inhibits (dis
-
ables) the output from the RF 2 Multiplexer with a
logic high.
Pin 11 RF CLK
The clock will control the synthesizer chip and
power control circuit when loading. This pin is a TTL
input from the Controller.
Pin 12 HS CS RX
Pin 12 is not used at this time.
Pin 13 RF MUX1 INH
The Multiplexer-1 Inhibit (U105, pin 6) is a
CMOS input from the Controller that inhibits (dis
-
ables) the output from the RF 1 Multiplexer with a
logic high.
Pin 14 V REF EX
This is the 3.5V reference to the Exciter TCXO.
3.5V from the Exciter is passed from J102, pin 9 to
this pin and the backplane. The voltage then passes
through the MAC and back to the backplane to J101,
pin 22 with the TX MOD. These are connected to
J102, pin 13 back to the Exciter.