Troubleshooting Table for Synthesizer
3-3
2.0
Troubleshooting Table for Synthesizer
Symptom
Possible Causes
Procedure
Corrective Action
Synthesizer Out of
Lock (RX mode
only)
1. VCO fault
Verify oscillator is working, check RF
level at U251-10 per schematic.
Check dc voltages at U251 pin 2
through 6 and 10 per
Board and IC
troubleshooting table
.
Verify steering line voltage is
between ~3V and 10V.
Check VCO tank components
connected to U251-5 and 6.
Check for shorts/opens, replace
U251.
Check D251 and associated
components.
2. Synthesizer fault
Verify TRB line (from U201-2 to
U251-19) is low in RX mode
Check for shorts, check U201
voltages per
Board and IC
troubleshooting table
, replace
U201 if incorrect.
3. Programming fault
Verify RX channel programming is
correct.
Re-program if necessary.
Synthesizer Out of
Lock (TX mode
only)
1. VCO fault
Verify oscillator is working, check RF
level at U251-10 per schematic.
Check dc voltages at U251 pins
1,3,4,10,15,16 per
Board and IC
troubleshooting table
.
Verify steering line voltage is
between ~3V and 10V.
Check VCO tank components
connected to U251-15 and 16.
Check for shorts/opens, replace
U251.
Check D261 and associated
components.
2. Synthesizer fault
Verify TRB line (U201-2 to U251-19)
is high (3V) in TX mode
Check for shorts, check U201
voltages per
Board and IC
troubleshooting table
, replace
U201 if incorrect.
3. Programming fault
Verify TX channel programming is
correct.
Re-program if necessary.
Synthesizer Out of
Lock (RX and TX
modes)
1. VCO fault
Check that RF level at U251-12 is at
least -12 to -20 dBm (UHF)
If low/missing, check L276,
C276-7, R276.
2. Synthesizer fault
Check that RF level at U201-32 is at
least -12 to -20 dBm (UHF).
Verify steering line voltage is
between ~3V and 10V.
If correct, check/replace U201.
If incorrect, check R248 and
C241.
Check loop filter components
R243-5 and C243-5.
3. DC voltage fault
Verify 4.5V dc at U201-28.
Verify 12.1V dc at U201-47
Check C231-233, etc., for
shorts. If OK check/replace
U201.
Check for 3V 1.05 MHz sq
waves at U201-14 and 15.
Check C218-228, D220-221.
4. Programming fault
Verify channel programming is cor-
rect.
Re-program if necessary.
Summary of Contents for CP 140
Page 1: ...Commercial Series CP140 CP160 CP180 Portable Radios Detailed Service Manual 6866550D20 O ...
Page 2: ...ii ...
Page 4: ...iv ...
Page 12: ...viii ...
Page 28: ...iv ...
Page 40: ...1 12 THEORY OF OPERATION ...
Page 48: ...2 8 TROUBLESHOOTING TABLES ...
Page 50: ...3 2 CONTROLLER KEYPAD SCHEMATICS ...
Page 58: ...3 10 Keypad Board Parts List 8466565A01 O ...
Page 62: ...iv ...
Page 66: ...1 4 MODEL CHART AND TECHNICAL SPECIFICATIONS ...
Page 90: ...3 16 TROUBLESHOOTING TABLES ...
Page 92: ...4 2 VHF PCB SCHEMATICS PARTS LISTS ...
Page 108: ...iv ...
Page 112: ...1 4 MODEL CHART AND TECHNICAL SPECIFICATIONS ...
Page 136: ...3 16 TROUBLESHOOTING TABLES ...
Page 138: ...4 2 UHF1 PCB SCHEMATICS PARTS LISTS ...
Page 154: ...iv ...
Page 158: ...1 4 MODEL CHART AND TECHNICAL SPECIFICATIONS ...
Page 182: ...3 16 TROUBLESHOOTING TABLES ...
Page 184: ...4 2 UHF2 PCB SCHEMATICS PARTS LISTS ...
Page 200: ...iv ...
Page 204: ...1 4 MODEL CHART AND TECHNICAL SPECIFICATIONS ...
Page 228: ...3 16 TROUBLESHOOTING TABLES ...