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TROUBLE SHOOTING
Item Symptom
Possible Cause
1
Unit does not turn on.
Defective power switches VR4.
Check the battery voltage.
Defective regulator U12.
2
Speaker no sound with
AF signal applied to
volume control
Defective volume control.
Defective speaker.
Defective U14 and/or associated components.
3
Squelch circuit inoperative
Check squelches control.
Defective U1 and/or associated circuitry between pin 9, 10 and 11.
4
UHF&VHF No receive (RX)
Defective regulator U12.
Defective regulator U14
Check second OSC 20.95MHz, pin9 of U2;
Defective Q6.
Check U1 audio output voltage at pin 9.
Defective F1 and F2;
5
Only UHF No receive (RX)
Check TP2 0.5 – 4.0V
Defective Q8, Q7.
Defective F6
6
Only VHF No receive (RX)
Check TP1 0.5 – 4.0V
Defective Q15, Q3.
Defective F1, F2
7
UHF&VHF Low receiver
sensitivity
Check antenna and connector for possible corrosion or bad connection.
Defective F3, F4
Defective U1
Check the output level of local OSC.
8
Only UHF Low receiver
sensitivity
Check antenna is a dual band type;
Failure of the output from Q7, Q8;
Defective F6;
9
Only VHF Low receiver
sensitivity
Check antenna is a dual band type;
Failure of the output from Q3, Q15;
Defective F1, F2;
10
UHF& VHF No transmit
(TX)
Defective PTT switch.
Defective regulator U12.
Check power transmits circuit Q1, Q2;
Check power control circuit Q33, Q38;
16
Summary of Contents for MR HH425 LI VP
Page 7: ...BLOCK DIAGRAM BACKLIGHT BACKLIGHT 7 ...
Page 11: ...Main PCB Top View Bottom View VR3 VR2 VC1 L44 L46 SQL L45 11 ...
Page 12: ...WIRING DIAGRAM CHARGER CHARGER 12 ...
Page 13: ...Main PCB Top View PRINTED CIRCUIT BOARD SQL 13 ...
Page 14: ...Main PCB Bottom View PRINTED CIRCUIT BOARD 14 ...
Page 15: ...Charger PCB PRINTED CIRCUIT BOARD Top View Bottom View LCD PCB Bottom View Top View 15 ...
Page 18: ...MAIN UNIT EXPLODED VIEW 18 ...
Page 19: ...CHARGER UNIT EXPLODED VIEW 19 ...
Page 20: ...BATTERY TRAY UNIT EXPLODED VIEW 20 ...
Page 48: ...U4 9032 HT D 48 ...
Page 49: ...U5 M38C29FFAHP60K 49 ...
Page 50: ...2 1 3 1 VOUT 2 VSS 3 VIN Delay Circuitry Vref VSS VOUT VIN U6 XC61FC4012MR U7 U8 U9 NJM324 50 ...
Page 51: ...1 2 3 4 8 7 6 5 A0 A1 A2 GND VCC WP SCL SDA U AT C N 11 24 16 U12 XC6204B502MR 51 ...