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Motorola Astro Digitalport Saber Troubleshooting 68p81076c10 A Manual

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Page 21

 
10-21 
Chart 33 . VHF/UHF Voltage Controlled Oscillator (VCO)
VCO TX/RX UNLOCK
Check
VDC at
C246
(VCTRL)
VDC
13V/0.7V/
Drifting
?
4.6V at
Collector
of Q202? Replace
U201
For VHF
check L217.
If OK
replace
U201.
Power at
collector of
Q202?
Voltage
at U204
Pin 21? Check
U2040.1V at
U201
Pin 7?
Is L207
(UHF) 208/209/
210/219
open?
0.7V at
U201 Pin
5?
Is
C235-C241,
CR207 (UHF)
CR201
open
Replace components & go
to -VEE crossover freq.
tune procedures Chart
C.39 except if L208, L209
are changed.
Check L205...

Page 22

 
10-22 
Chart 34 . 800MHz Voltage Controlled Oscillator (VCO)
VCO TX/RX Unlock
MAEPF-24388-A
NO
VDC 
U307-9
VDC
U302-19
VDC
U302-20
VDC 
U302-17 NO YES
Check Continuity
Between 
U302-19 &
U307-9
YES NO NO YES
5VDC
U307-3
777-825MHz
Change U302
5VDC
U303-6
806-825MHz
VDC
U303-3, 13
NO
YES
YES NO
5VDC
U307-8
850-870MHz
Measure
Freq.
U303-15
Measure
Freq.
U302-21
Refer to FGU
Chart C.32
VDC
U307-1, 7
Change U307
5VDC
U302-38
806-825MHz
Check Continuity
Between
U302-38 & U303-6
Refer to FGU
Chart C.32
YESNO...

Page 23

 
10-23 
Chart 36 . VHF/UHF DC Switch
No R5
U106 Pin 2Voltage
at U106
Pin 8?Voltage
at Q107,
Pin 2?Voltage
at Q107,
Pin 3?Voltage
at Q107,
Pin 4?
7.5V at
U202
Pin 8?5V at
U102
Pin 1?Less
than 4.8V
 at U106 
Pin 3?
Replace
U106
Check DC Power
Supply Failure
Chart C.5Replace
Q107 Check L131,
L121 and CR109
and L122 For 
Open Connections
YES
YES
YESYES
YES
NO
YES NO
NO
YES
NO NONO
Replace
U102
Replace
U202
No T5Voltage
at Q111 Pin
 3 collector?Voltage
at U202,
Pin 8?
Replace
U102Go to
Chart C.26
Replace...

Page 24

 
10-24 
Chart 37 . 800MHz Transmitter RF
No/Low Power
Replace
Ant Switch
YES
NO
Check
Continuity at
Ant. Switch
NO BAD BAD GOODGOOD GOOD BAD
Check L102,
L105, C114,
C101, C108
Replace U501
Go to VCO
Chart C.34
Go to DC Switch 
Chart C.35
NO
YESCheck E1, E2,
E3, E4, J3
Check Q502
& R509
Go to VCO
Chart #5B
Replace U502
Check R507,
R508 NOYES
YESNO
NO YES NO
YES NO
YES YES YES
NO NO
YES YES
NONONO
GOOD
YES
NO
Check U503
D/A ICVDC
U502-2, 50.37 VDC
U504-12 VDC
U502-1 VDC
U502-3, 4 VDC
Base Q501 VDC
U502-7...

Page 25

 
10-25 
Chart 38 . VHF/UHF Transmitter RF
No/Low Power
TX Current
> 500 mA?
RF at RF
Connector,J2
Pin 2?
Replace U105
NOYES
RF at 
Cathode of
CR108?RF Present
at Anode
of CR108?RF Present
at Pin 5 of
U104?
Replace U104Check Antenna
Switch Biasing
Circuits, L122,
L105, U101Check Components
Between C147
and L128Check antenna
switch
YES
YES
YES
YESNO
NO
NO
Is T5 On
at C153?B+ at 
U105, Pin 5
(VHF)
5,6 (UHF)?
Replace U105
7.5V at
U105
Pin 2.4?Voltage
at U105
Pin 3?RF Voltage
at U105,
Pin  1?
Check...

Page 26

 
10-26 
Chart 39 . VHF/UHF Only, VCO Crossover Frequency Tune
VCO-VEE Crossover
Freq. Tune ProcedureProgram Radio to 
Low Band Edge 
136 MHz (VHF)
403 MHz (UHF1)
450 MHz (UHF2)
Is
VCTRL (TP5)
>3.0V?YES
MAEPF-23274-B
NO
Program Radio to 
High Band Edge
178 MHz (VHF)
470 MHz (UHF1)
520 MHz (UHF2)
Is
VCTRL
>11.0V?
Program the New 
Crossover Frequency 
into the CodeplugIs 
VCTRL
2.5V to 3.5V?
Replace C240 or C223 
*
Use Up/Down Buttons
to Tune Crossover 
Frequency w/RSS
VHF
3.0
2.7UHF1
2.7
2.4UHF2
2.7
2.7...

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