Main Synthesizer Troubleshooting - Motorola MTM800 User Manual

TROUBLESHOOTING CHARTS: 450-470MHz

Main Synthesizer Troubleshooting

Failure:
RX injection frequency error greater than 2 kHz or unstable frequency.
Main VCO frequency error at TP5702 greater than 2 kHz or unstable
frequency 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 386.675MHz
Spectrum Analyser
Set Reference Level to 10dBm
Run Tetra Com script for RX Test
Measure RF levels and frequencies with the 50 ohms RF probe.
Measure DC levels with a multimeter.
C5316 about 13.5V
>8V and frequency
U5331 pin 32 about
C5343 about 4.6V
Start
Replace U5331
No
DC at
R5315 and R5316
measured with
?
DC
at TP5701
No
<1V and frequency at
at U5331 pin 32
U5331 pin 32
>331.675MHz
<331.675MHz
?
Yes
Yes
No
RF level at
TP5702 about -5dBm
-5dBm
?
Yes
Yes
Check components
between TP5702
and U5331 pin 32
No
DC at
Replace U5331
?
Yes
Replace U5331
Tetra Com Script for RX Test
TEST_ENTER
DELAY 18
Check for "Radio HW is READY"
MODE IDLE
FREQ RX 460.025
L1TIMER ON
AVE 10
MODE RSSI
GO
Use STOP to terminate RSSI reading
No
3Vp-p
1.05MHz at Yes
Check D5301, D5302,
R5312 and connected
components.
scope
?
DC
at TP5701
No
Check components
between U5701
pin 5 & 6 and TP5701.
?
No
RF level at
No VCO output signal!
Go to Main VCO Chart.
?
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