TROUBLESHOOTING CHARTS (800MHz) MTM700
Mobile Radio / Detailed Service Manual
9.2 - 17
Synthesizer & VCO Troubleshooting
NO
NO
Is the
frequency
787.175 MHz
@ +3dBm
YES
Measure the RF level at the pres-
caler input on C5338.
YES
Is the frequency at
TP5701 787.175 MHz
@ -0dBm
NO
Synthesizer and RX VCO are
OKAY.
For TX issues check Escort. For RX
issues check Receiver.
Problem still
exists?
YES
YES
Are bias volt-
ages
correct?
NO
YES
Is voltage at
C5301
@ about 5.3V?
Make sure U5701 is pow-
ered (5V on pins 14 and
18), and the surrounding
components are in place.
Measure Q5712 bias volt-
ages:
• Base 2.3V,
• Collector 4.3V, and
• Emitter 1.7V.
Fix problem with
Q5712, or bias
components.
Check Loop filter components (C5305,
R5304, C5305, R5302, and C5301).
Is RXH Line
@ 5V?
YES
Measure the RF
level at TP5701.
Make sure Pin 19 and 20 of
U5701 are close to 0V.
Check C5740.
Replace U5701.
Is 787.175 MHz
present at pin 8
of U5701?
Measure Q5701 bias
voltages:
• Base 0.7V,
• Collector 3.3V,
• Emitter 0V.
Fix problem with
Q5701, or bias com-
ponents.
NO
YES
Check Q5301 for solder-
ing defects. Make sure
that Pin 48 of U5331 is
@ 5V.
NO
Tetra Com Script for Rx Test:
TEST_ENTER
DELAY 10
Check for “Radio HW is Ready”
MODE IDLE
FREQ RF 860.525
L1TIMER ON
AVE 10
MODE RSSI
GO
Use STOP to terminate RSSI reading
Summary of Contents for MTM700
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