Service manual
ALIGNMENT PROCEDURES
The
MRS
904 alignment procedures require the following test equipment:
•
DC
Power Supply (13.6V)
• Oscilloscope
•
RF Wattmeter
• AF Signal Generator
• RF Dummy Load, 50 Ohms
•
RF Signal Generator
•
DC
Voltmeter
•
Deviation Meter
• Distortion Meter
• Frequency Counter
Set up this test equipment as shown in figure
11
.
R F SIGNAL
ANTENNA
RF
RF DUMMY
GENERATOR
RX
TX
'-----
WATIMET
ER
'---
LOAD (SOQ)
MRS 904
RADIO
DC POWER
FREQUENCY
SUPPLY
MIC
COUNTER
(13.6
V)
PIN
PIN
3
4
1
DC
AF SIGNAL
DEVIATION
AUDIO
VOLTMETER
METER
GENERATOR
~GROUND
l
OSCILLOSCOPE
Figure 11. Test Equipment Setup
NOTES
There are no receiver adjustments/alignments.
1.
Before you begin this procedure, make sure
that
J1
05 on the Motherboard is
in
the "900"
position.
2.
If you are using the Trunking Version (MRS
904T), Make sure that J101 is in the "T" po-
sition. If you are using the Conventional
Version (MRS 904S), Make sure that
J1
01
is
in the
"C" position.
DISTORTION
METER
EXTERNAL DC POWER SUPPLY
ADJUSTMENT
1. Turn the external
power
supply
on
.
2.
Connect a DC voltmeter to the output of the exte
rn
al
power supply.
3. Adjust the voltage cont
ro
l on the external power
supply to an output between 13.6 and 13.8
VDC.
LOCAL AUDIO AND SQUELCH
ADJUSTMENTS
1.
Set the VOLUME control to its physical midpoint and
rotate the SQUELCH control fully counterclockwise.
2.
Input a strong RF signal (-47dBm) into the repeat
er.
Modulate this signal with a 1000 Hz tone at 1.5 kHz
deviation.
Page
29
MRS 904
1/1/90
Motherboard
•
Logic Board
~
;
Relay Board
Figure 12. MRS 904 Open View