Troubleshooting
68P02963C70-O
3 - 25
Second LO VCO Test
Perform the following:
1.Remove the 2nd_LO shield.
2.Set the Unit to continuous
Recieve mode (Rxndc).
3.Measure the 2nd_LO control
voltage at C761.
Measure the RF power level at
C959 at 219.3MHz.
The 2nd_LO VCO/synthesizer
is O.K.
Chek for feedback
problem:
1.check soldering of
C262,R951,C970.
2.Measure the RF power
level at Pin 5 of the LMX
at 219.3MHz.
Check Q905,
R939 for soldering
problems and for
the right values.
(compare with BOM)
No
Check DC supply for the VCO:
1.Check for SF_OUT on C902,
R939,R906.
2.Check for TETRA_2nd_LO_En on
Q910.
Check DC Block
No
Check DC supply for the LMX:
1.Check for 5V_RF on C954
or on Pin 22 of the LMX.
2.Check 2.775V_RF on Pin
23 and Pin 24 of the LMX.
Yes
Check DC Block
No
Perform VCO_ONLY TEST:
1.connect an external 0.5 to 4.5V
power supply to R9016.
2.Measure the RF freq at C959.
3.Adjust the external supply voltage
until the frequency is219.3MHz.
The VCO is working properly.
the problem is with the LMX.
Replace the LMX.
Yes
Check R915,C903,
C948,R916,D902,
C960,L905,C940,
C920,R909,R906,
C922,C921,R922,
R939,R906,C953,
C959 for soldering
problems and
compare with BOM
values.
No
Is the control Voltage at R916 and
C948
between 0.5 and 4.5Vdc
Is the power level at 0
dBm
and stable on frequency.
No
Does the VCO has
its DC Supply?
Does the LMX has its
DC Supply?
Can the frequency
be set to
219.3MHz?
Yes
Yes
TetraCom Commands:
WPIC 3 9 1b NOW
dual RF 0202a2 004447
Yes
Yes
Summary of Contents for MTH500
Page 10: ...Contents x 68P02963C70 O THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 14: ...Foreword xiv 68P02963C70 O THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 18: ...Overview 1 4 68P02963C70 O THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 50: ...Theory of Operation 2 32 68P02963C70 O THIS PAGE INTENTIONALLY LEFT BLANK ...
Page 76: ...Troubleshooting 3 26 68P02963C70 O Offset VCO Test ...
Page 78: ...Troubleshooting 3 28 68P02963C70 O This page left blank intentionally ...
Page 82: ...Programming the Radio 4 4 68P02963C70 O This page left blank intentionally ...
Page 100: ...Maintenance 5 18 68P02963C70 O Figure 23 Exploded View 1 2 3 4 5 7 6 X6 8 ...
Page 101: ...Maintenance 68P02963C70 O 5 19 Figure 24 Exploded View of Chassis Assembly 9 12 13 10 11 14 ...
Page 102: ...Maintenance 5 20 68P02963C70 O ...
Page 134: ...SCHEMATIC DIAGRAMS MTH500 Flex CD 6 32 68P02963C70 O This page left blank intentionally ...
Page 140: ...Replacement Parts and Kits 6 68P02963C70 O ...
Page 141: ...Replacement Parts and Kits 68P02963C70 O 7 ...
Page 142: ...Replacement Parts and Kits 8 68P02963C70 O ...
Page 144: ...Test Equipment Service Aids Tools A2 2 68P02963C70 O THIS PAGE INTENTIONALLY LEFT BLANK ...