Motorola CP160 Service Information - Page 21

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Also for Motorola CP160: User Manual (46 pages), Basic User's Manual (16 pages), Basic User's Manual (16 pages), Basic User's Manual (18 pages), Detailed Service Manual (28 pages), Cps/Tuner Installation Manual (6 pages), Service Information (46 pages)

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Troubleshooting Table for Transmitter

Symptom

Poor TX range,

1. RF test jack defective

conducted power

2. Antenna matching net-

work fault

3. Defective or wrong

antenna

No internal mic

1. Mic bias fault

audio (EXT MIC

audio OK)

2. Defective mic

3. Defective mic jack

No EXT MIC audio 1. Mic bias fault

2. Audio path fault

3. Defective audio acces-

sory

Possible Causes

Procedure

Verify continuity of J140 pins 3 and 4

in RX mode only.

Visually inspect components C140-

141, L140 or L141. Check dc conti-

nuity of L140 or L141in RX mode

only.

Verify correct antenna is installed.

Try another antenna.

Verify U451-35 is low when side PTT

is pressed.

Verify Q470-6 is high when side PTT

button is pressed.

Verify approx 1.8V dc across car-

tridge when side PTT button is

pressed. Verify audio present (~10

mV rms) when speaking into mic.

Verify continuity between J471 pins

4 and 5.

Verify approx 1.8V dc across EXT

MIC cartridge in TX mode. Verify

audio present (~10 mV rms) when

speaking into mic.

Verify mic audio present (~10 mV

rms) at U451-46.

Verify amplified mic audio present

(~200 mV rms) at U451-40.

Try another accessory.

Corrective Action

Replace J140.

Repair/replace if necessary.

Replace antenna.

Check/replace U451.

Check/replace R474, R476, and

Q470.

Check mic connector and R478.

Replace mic cartridge.

Replace J471.

Check Q470. R475, R477,

L471. Check VR473, VR475,

D470 for shorts.

Check L471, C470.

Check/replace U451.

Replace defective accessory.

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