Motorola ASTRO Digital Saber Service Manual page 104

VCO TX/RX Unlock
VDC VDC
NO NO
U307-9 U302-19
YES
YES
Check Continuity
Between
U302-19 &
U307-9
5VDC 5VDC
YES YES
U307-3 U307-8
777-825MHz 850-870MHz
NO
NO
5VDC
NO
U303-6
806-825MHz
YES
VDC
U303-3, 13
NO
YES
Change U302
Chart 34 . 800MHz Voltage Controlled Oscillator (VCO)
VDC VDC
YES
U302-20 U302-17
NO NO
Refer to
Check C310 if
Chart DC
OK Change
Switch C.37
U302
Measure
Measure YES YES
Freq.
Freq.
U302-21
U303-15
NO NO
Check L301,
C377 if OK
VDC
NO
Change U303
U307-1, 7
YES
Refer to FGU
Chart C.32
Change U307
5VDC
NO
U302-38
Refer to FGU
806-825MHz
Chart C.32
YES
Check Continuity
Between
U302-38 & U303-6
MAEPF-24388-A
800MHz DC Switch.
Yes
0V at Q503
Pin 5 - RX
Pin 3 - TX?
Yes
Check U503.
VDC at U305?
VDC at J1-17?
Refer to Chart
C.5 on "DC
Supply Problem".
Chart 35 . 800MHz DC Switch
10-22
Voltage at
Q503-4?
No
Check
Yes
Voltage at
continuity
U305-1?
between U305
and Q503.
No
Yes
Replace U305.
No
Check mating
No
plug. If plug is
good, go to
chart C.26.
Yes
MAEPF-24392-A