Motorola MTM700 Detailed Service Manual page 289

TROUBLESHOOTING CHARTS (400MHz)
Tx Frequency Generation Troubleshooting
Failure:
No or low TX LO signal level.
TX frequency error greater than 2 kHz or unstable after
frequency tuning.
Connect the radio's accessory connector to the Tetra Com
interface.
Connect the radio's antenna connector to the high power
RF output on the IFR.
Connect the 50 ohms RF probe to the low power RF input
on the IFR
Setup IFR:
Select high power output and low power input
No System,
TX Test,
TX Frequency 429.925MHz
Spectrum Analyser
Set Reference Level to 10dBm
Run Tetra Com script for TX FGU Test
Measure RF levels and frequencies with the 50ohms RF probe.
Measure DC levels with a multimeter.
Check transistor stage
Q5621 and switch
Q5301
No
RF level
at Q5621 Collector
about 0dBm and DC
about 3.9V
?
Yes
Check components
between
Q5621 and C5837
Check components
U5601, D5601- D5604 and
associated components
Check transistor stage
Q5671 and 5V source
U5322
Check transistor switch
Q5301 bevor replacing
Q5602
MTM700 Mobile Radio / Detailed Service Manual
Start
Yes
RF level
frequency stable at
at C5804 about
429.925MHz
0dBm
?
No
Yes
RF level at
>7V and frequency
Q5601 Emitter
about 0dBm >429.925MHz at
?
Yes
No
RF level at
Q5631 Collector
about 0dBm
Yes
1.4V DC at
Yes
Q5601 Emitter
?
Set IFR TX Frequency
to 429.925 * 0.8 MHz
No
No
4.3V DC at
level at R5707 about
Q5671 Emitter
?
Yes
Yes
No
2.1V DC at Q5602
Collector
?
Yes
Check DC path of
stage Q5601 before
replacing Q5601
frequency correct and
Yes
Before replacing U5702 check
transistor stage Q5681, Q5651,
3.3V at U5702 pin 15,
components between Q5631
collector and U5702 pin 16.
Tetra Com Script for TX FGU Test
TEST_ENTER
DELAY 10
Check for "Radio HW is READY"
MODE IDLE
INTR DIS
FREQ TX 429.925
L1TIMER ON
TX POW 4
RFTON ATT 0.5
RFTON FRQ 0
RFTON CHN I
FEEDBACK OPEN
MODE RFTONE
Use MODE IDLE to terminate transmit mode
OK
Yes
Is
Check components
U5601, D5601- D5604
and associated components.
?
No
No
DC
DC
at R5653
at R5653
No
<1V and frequency
< 429.925MHz at
C5837
C5837
?
?
Yes
No
Check transitor stage Q5631
?
No
RF
2.7V DC at
U5701 pin 19 & 20
0dBm
?
?
Yes
RF level at
TP5702 about
-5dBm
?
Yes
Before replacing U5701
check
R5706, R5707, C5706
No
Is
FGU failure!
Go to Main Synthesizer Chart
stable
?
No
Check transitor switch
Q5301, U5322, U5331
No
No Main VCO signal
Go to Main VCO Chart
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