Motorola APX 1000 Detailed Service Manual page 149

Troubleshooting Charts: VCO Failure
VCO Failure – Page 6 (900 MHz)
5
Control voltage
at R705
0.3<Vdc<10.6?
Yes
At Tx, is L3007 high and
L3012 low?
or
At Rx, is L3007 low and
L3012 high?
Yes
At Tx, is Vdc at pin 2 of
Q3038 > 0.7V?
or
At Rx, is Vdc at pin 2 of
Q3062 > 0.7V?
Yes
At Tx, check and visual inspect VR3010,
VR3006, VR3008, VR3009, C3014, C3015,
C3022, C3023, Y3020.
At Rx, check and visual inspect VR3048,
VR3011, VR3013, VR3014, C3050, C3051,
C3054, C3055, Y3053.
No
Take continuity
No
check of traces to
U702.
No
At Tx, is Vdc at R3030 =
4.55V?
No
or
At Rx, is Vdc at R3058 =
4.55v?
Yes
At Tx, replace Q3038.
At Rx, replace Q3062.
Is Vdc at C742 5V,
No
Vdc at C726, C734,
C737 2.775V?
Yes
No
Is Vdc at Y701
pin 4 2.775V?
Yes
16.8MHz at pin
No
3 of Y701 and
C736?
Yes
No
16.8MHz at
L753?
Yes
No
Yes
10.8Vdc at pin2
of D723?
No
Yes
2.775Vdc at pin
4 of D722?
Check 2.775V and
5V supply.
Check 2.775V
supply.
Replace Y701
and/or C736.
Check and visual
Yes
inspect U746 circuitry.
Fault found?
No
Replace U702.
Check D722, D723,
C716, C717, C718,
C719.
5-51
Replace the
suspected
components.