Troubleshooting Table for Transmitter
3-5
Poor TX range,
conducted power
OK
1. RF test jack defective
Verify continuity of J140 pins 3 and 4
in RX mode only
.
Replace J140.
2. Antenna matching net-
work fault
Visually inspect components C140-
141, L140 or L141. Check dc conti-
nuity of L140 or L141
in RX mode
only
.
Repair/replace if necessary.
3. Defective or wrong
antenna
Verify correct antenna is installed.
Try another antenna.
Replace antenna.
No internal mic
audio (EXT MIC
audio OK)
1. Mic bias fault
Verify U451-35 is low when side PTT
is pressed.
Verify Q470-6 is high when side PTT
button is pressed.
Check/replace U451.
Check/replace R474, R476, and
Q470.
2. Defective mic
Verify approx 1.8V dc across
cartridge when side PTT button is
pressed. Verify audio present (~10
mV rms) when speaking into mic.
Check mic connector and R478.
Replace mic cartridge.
3. Defective mic jack
Verify continuity between J471 pins
4 and 5.
Replace J471.
No EXT MIC audio 1. Mic bias fault
Verify approx 1.8V dc across EXT
MIC cartridge in TX mode. Verify
audio present (~10 mV rms) when
speaking into mic.
Check Q470. R475, R477,
L471. Check VR473, VR475,
D470 for shorts.
2. Audio path fault
Verify mic audio present (~10 mV
rms) at U451-46.
Verify amplified mic audio present
(~200 mV rms) at U451-40.
Check L471, C470.
Check/replace U451.
3. Defective audio
accessory
Try another accessory.
Replace defective accessory.
Symptom
Possible Causes
Procedure
Corrective Action
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 ...