Troubleshooting Flow Chart
UHF3 (350
–
400 MHz)
34
Check RX circuit
Q920 outputs 9V3A?
Check the power-on
circuit
No
Q902 outputs 9V1A?
Yes
Check Q902 and
Q903
No
Front panel output is
normal? [1]
Yes
Replace the front
panel
No
Input an IF signal (73.35
MHz) and test whether the
circuit is normal?[2]
Yes
Second LO is normal?
[3]
No
Check Q701 and
peripheral
components
No
TP707 receives a
18 MHz signal?
Check D702 and
relevant
components
Yes
No
TP6101 output is
normal?[4]
Yes
TP6106 output is
normal?[5]
Yes
No
Check RX VCO and
LO amplifier
No
Check D6106, T6100,
T6101, and peripheral
circuits
Sensitivity at TP6104 is
normal?[6]
Yes
Yes
Check Q6102, D6103,
D6104, and peripheral
circuits
Check L809, L813,
M801, and peripheral
circuits
Yes
No
End
Sensitivity at TP6103 is
normal?[7]
Check Q6100, D6101,
D6102, and peripheral
circuits
No
Yes
Description of normal situations:
[1] During sensitivity test, use a communication test set to demodulate the audio signal at TP4012 and
TP4016. If the signal is demodulated normally, it is concluded that the front panel is defective.
[2] Use the communication test set to apply a 73.35 MHz IF signal at the mixer, and sensitivity is about
-110 dBm.
[3] There is a second LO signal (71.1MHz) at TP704.
Содержание MD78X
Страница 1: ...DIGITAL MOBILE RADIO SERVICE MANUAL...
Страница 5: ...UHF1 400 470 MHz...
Страница 14: ...UHF1 400 470 MHz Exploded View and Packing Guide 7 3 2 Packing Guide...
Страница 56: ...UHF1 400 470 MHz Interface Definition 49 Pin No Name Description 39 GND Grounding 40 PWB_IN Power On Off signal...
Страница 62: ...55 9 PCB View MD78X MD78XG PCB View Front Panel Top Layer...
Страница 63: ...56 MD78X MD78XG PCB View Front Panel Bottom Layer...
Страница 64: ...MD78X MD78XG PCB View Main Board Top Layer 57...
Страница 65: ...MD78X MD78XG PCB View Main Board Bottom Layer 58...
Страница 111: ...UHF2 450 520 MHz...
Страница 120: ...UHF2 450 520 MHz Exploded View and Packing Guide 7 3 2 Packing Guide...
Страница 167: ...54 9 PCB View MD78X MD78XG PCB View Front Panel Top Layer...
Страница 168: ...55 MD78X MD78XG PCB View Front Panel Bottom Layer...
Страница 169: ...MD78X MD78XG PCB View Main Board Top Layer 56...
Страница 170: ...MD78X MD78XG PCB View Main Board Bottom Layer 57...
Страница 216: ...UHF3 350 400 MHz...
Страница 225: ...UHF3 350 400 MHz Exploded View and Packing Guide 7 3 2 Packing Guide...
Страница 272: ...54 9 PCB View MD78X MD78XG PCB View Front Panel Top Layer...
Страница 273: ...55 MD78X MD78XG PCB View Front Panel Bottom Layer...
Страница 274: ...MD78X MD78XG PCB View Main Board Top Layer 56...
Страница 275: ...MD78X MD78XG PCB View Main Board Bottom Layer 57...
Страница 321: ...UHF5 806 941 MHz...
Страница 330: ...UHF5 806MHz 941MHz Exploded View and Packing Guide 7 3 2 Packing Guide...
Страница 376: ...53 9 PCB View MD78X MD78XG PCB View Front Panel Top Layer...
Страница 377: ...54 MD78X MD78XG PCB View Front Panel Bottom Layer...
Страница 378: ...55 MD78X MD78XG PCB View Main Board Top Layer...
Страница 379: ...56 MD78X MD78XG PCB View Main Board Bottom Layer...
Страница 414: ...VHF 136 174 MHz...
Страница 423: ...VHF 136MHz 174MHz Exploded View and Packing Guide 7 3 2 Packing Guide...
Страница 468: ...PCB 52 9 PCB View MD78X MD78XG PCB View Front Panel Top Layer...
Страница 469: ...PCB 53 MD78X MD78XG PCB View Front Panel Bottom Layer...
Страница 470: ...MD78X MD78XG PCB View Main Board Top Layer 54...
Страница 471: ...PCB 55 MD78X MD78XG PCB View Main Board Bottom Layer...