Motorola MTM800 - Tx Frequency Generation Troubleshooting

TROUBLESHOOTING CHARTS: 450-470MHz 9.1 - 17
Tx Frequency Generation Troubleshooting
Check transistor stage
Q5621 and switch
Q5301
RF level
at Q5621 Collector
about 0dBm and DC
about 3.9V
?
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
Check DC path of
stage Q5601 before
replacing Q5601
Before replacing U5702 check
transistor stage Q5681, Q5651,
3.3V at U5702 pin 15,
components between Q5631
collector and U5702 pin 16.
FGU failure!
Go to Main Synthesizer Chart
Before replacing U5701
check
R5706, R5707, C5706
Is
frequency correct and
stable
?
RF level at
TP5702 about
-5dBm
?
2.7V DC at
U5701 pin 19 & 20
?
RF
level at R5707 about
0dBm
?
Set IFR TX Frequency
to 469.925 * 0.8 MHz
RF level at
Q5631 Collector
about 0dBm
?
Check transitor stage Q5631
DC
at R5653
<1V and frequency
< 469.925MHz at
C5837
?
DC
at R5653
>7V and frequency
>469.925MHz at
C5837
?
Check components
U5601, D5601- D5604
and associated components.
Is
frequency stable at
469.925MHz
?
RF level
at C5804 about
0dBm
?
RF level at
Q5601 Emitter
about 0dBm
?
1.4V DC at
Q5601 Emitter
?
4.3V DC at
Q5671 Emitter
?
2.1V DC at Q5602
Collector
?
No Main VCO signal
Go to Main VCO Chart
Check transitor switch
Q5301, U5322, U5331
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Failure:
No or low TX LO signal level.
TX frequency error greater than 2 kHz or unstable after
frequency tuning.
Tetra Com Script for TX FGU Test
TEST_ENTER
DELAY 18
Check for "Radio HW is READY"
MODE IDLE
INTR DIS
FREQ TX 469.925
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
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 469.925MHz
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.
Start
OK
ZWG0130967-O
6866539D31.book Page 17 Tuesday, March 20, 2007 6:32 PM