Motorola MTM800 - Main Synthesizer Troubleshooting

TROUBLESHOOTING CHARTS: 450-470MHz 9.1 - 19
Main Synthesizer Troubleshooting
Start
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.
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
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.
DC at
C5316 about 13.5V
?
3Vp-p
1.05MHz at
R5315 and R5316
measured with
scope
?
DC
at TP5701
>8V and frequency
at U5331 pin 32
>331.675MHz
?
DC
at TP5701
<1V and frequency at
U5331 pin 32
<331.675MHz
?
RF level at
U5331 pin 32 about
-5dBm
?
RF level at
TP5702 about -5dBm
?
Check components
between TP5702
and U5331 pin 32
Replace U5331
DC at
C5343 about 4.6V
?
Replace U5331
No VCO output signal!
Go to Main VCO Chart.
Check components
between U5701
pin 5 & 6 and TP5701.
Check D5301, D5302,
R5312 and connected
components.
Replace U5331
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
6866539D31.book Page 19 Tuesday, March 20, 2007 6:32 PM