Motorola APX 1000 Detailed Service Manual page 800

5-44
VCO Failure – Page 3 (700/800 MHz)
2
Control voltage
at R705
0.3<Vdc<10.6?
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,
Vdc at Q3039 4.55V?
Yes
At Tx 764-776MHz, Rx 851-870MHz, check and visual
inspect VR3010, C3014, C3015, C3022, C3023, Y3020.
At Tx 851-870MHz, Rx 764-776MHz, check and visual
inspect VR3048, C3050, C3051, C3054, C3055, Y3053.
At Tx 794-824MHz, check and visual inspect VR3011,
C3016, C3017, C3024, C3025, Y3021.
Is Vdc at C742 5V,
No
Vdc at C726, C734,
C737 2.775V?
Is Vdc at Y701
pin 4 2.775V?
Take continuity
check of traces to
U702.
No
16.8MHz at pin
3 of Y701 and
C736?
No
16.8MHz at
L753?
No
10.8Vdc at pin2
of D723?
2.775Vdc at pin
4 of D722?
Troubleshooting Charts: VCO Failure
No
Check 2.775V and
5V supply.
Yes
No
Check 2.775V
supply.
Yes
No
Replace Y701
and/or C736.
Yes
Check and visual
No
inspect U746 circuitry.
Fault found?
Yes
Yes
Replace U702.
No
Check D722, D723,
Yes
C716, C717, C718,
C719.
Replace the
Yes
suspected
components.
No