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Maintenance: 900 MHz Troubleshooting Charts 8-55

8.17.4 Troubleshooting Flow Chart for Receiver (for PCB 8485910Z01) (Sheet 2 of 2)

RF Signal at

the input of

FL300?

IF Signal at

L353?

RF Signal at

pin 8 of U301?

RF Signal at

CR300?

No or

Check harmonic filter L101 &

L102 CR101, CR102, and

CR300

Inject RF into J101

Yes

Check RF amp

(Q302) Stage.

Replace filter

FL301

Yes

Check U301, R320,

R321, R322.

Yes

1st LO O/P

OK?

Locked?

Yes

Check FGU

Yes

Trace IF signal from

L353 to U352.

Check for bad XTAL

filter

Yes

Is the level of the

IF signal of the

output of U352 as

indicated?

Before replacing

U351, check U351

voltages; trace IF

signal path

Yes

Is the biasing of

U352 OK?

Is R5 present?

Check Q210, U201

(pin 48) voltages

and U247

Yes

weak RF

RF Signal at

C317?

Replace

U352

Are the

AGC voltages

without RF as

indicated?

Yes

Check U302,

U350, and CR301

Replace

FL300

No or

weak RF

Default Chapter2
Chapter 1 Introduction25
Chapter 2 Radio Power Distribution29
- Figure 2-1. DC Power Distribution Block Diagram29
Chapter 3 Keypad31
Chapter 4 UHF Band 1 Theory of Operation35
Chapter 5 UHF Band 2 Theory of Operation43
Chapter 6 VHF Theory of Operation51
Chapter 7 Low Band, 800 Mhz, Passport & 900 Mhz Theory of Operation63
Chapter 8 Maintenance91
Chapter 9 Schematic Diagrams, Overlays, and Parts Lists151

Battery Type	Li-Ion
Waterproof	IP54
Operating Temperature	-30°C to +60°C
Frequency Range	VHF: 136-174 MHz
Number of Channels	16

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