Motorola GM140 Service Information - Page 26

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3-4

Troubleshooting Flow Chart for 25W Transmitter (Sheet 2 of 3)

2.1

Check S3440,

R3442 and R3443

Check Components bet-

ween U3402-2 Pin7 and

Q3421. Check Resistive

Network at Pins 5 & 6

before replacing Q3421

Voltage at

U3402-1 Pin

3 = 8.8V?

YES

Measure DC Voltage at Pin 2 & 3 of U3401

Check Q3442 and

Resistive Network at

U3402-1 Pin 3

before replacing

U3401

DC Voltage at

U3402-2 Pin

5 <8.8V?

YES

Check Q3422

Check PA Stages

No or too low Power when keyed

DC Voltage

at U3501

Pin 23 =0?

YES

<2V

DC Voltage

at U3402-1

Pin 1?

2-6

Pin 2 Voltage

0.62 *

Voltage at

Pin 1?

YES

Pin 3 Voltage

0.51 *

Voltage at

Pin 1?

YES

<2V DC Voltage at

>6V

U3402-2 Pin

2-6V

Check Final PA Stage

TROUBLESHOOTING CHARTS

If U3201 Pin 2 is high,

replace PCIC

Check Resistive Net-

work at Pins 2 & 3 of

U3402-1 before repla-

cing U3401

Replace U3401

Check Components

between U3402-2 Pin7

and Q3421. Check

Resistive Network at

Pins 5 & 6 before repla-

cing Q3421