Motorola APX 3000 Detailed Service Manual page 130

5-40
VCO Failure – Page 3 (7/800MHz)
2
Control
voltage at
Yes
At Tx 764-776MHz, Rx 851-870MHz, is
R3018 high?
or
At Tx 851-870MHz, Rx 764-776MHz, is
R3052 high?
or
At Tx 794-824MHz, is R3019 high?
Yes
At Tx 764-776MHz, Rx 851-870MHz, is
Vdc at Q3038 4.55V?
or
At Tx 851-870MHz, Rx 764-776MHz, is
Vdc at Q3062 4.55V?
or
At Tx 794-824MHz,
Yes
At Tx 764-776MHz, Rx 851-870MHz, check and
visual inspect VR3010, VR3003, VR3012,
VR3013, C3014, C3015, C3022, C3023, Y3020.
At Tx 851-870MHz, Rx 764-776MHz, check and
visual inspect VR3048, VR3017, VR3020,
VR3021, C3050, C3051, C3054, C3055, Y3053.
At Tx 794-824MHz, check and visual inspect
VR3011,VR3004, VR3014, VR3015, C3016,
C3017, C3024, C3025, Y3021
Is Vdc at C742 5V,
No
Vdc at C726,
C734, C737
Yes
Is Vdc at Y701
pin 4 2.775V?
Take continuity
check of traces to
No
Yes
16.8MHz at
pin 3 of Y701
No
Yes
16.8MHz at
L753?
Yes
10.8Vdc at
No
pin 2 of D723?
2.775Vdc at
pin 4 of D722?
Troubleshooting Charts: VCO Failure
Check 2.775V and
No
5V supply
Check 2.775V
No
supply
Replace Y701
No
and/or C736
Check and visual
inspect U746
No
circuitry. Fault
found?
No
Yes
Replace U702
No
Check D722,
Yes
D723, C716
Replace the
Yes
suspected