Motorola MTX series Theory/Troubleshooting Manual

42
TROUBLESHOOTING FLOW CHART #5A
(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
U204
0.1V 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 #9
except if L208, L209 are
changed.
Check L205 &
R220. If no fault
found, replace
U201.
3.3V
between
C2118 &
C212?
Check
L221 &
U204
Check
R203, R204,
R205, R209,
& Q202
Replace
U201
Replace
U201
Replace
U201
Check
L221 &
U204
4.4V at
U201 Pin
5?
Is
C219, C220,
C222, C223,
C226, C227,
C270, CR203
open
0.1V at
U201
Pin 14?
Is
L215, L216,
L211, L213,
open
Voltages
at U201 Pin
11 & 12
OK?
Check
R23, R206,
R217, R219
& R210
Replace components & go
to -VEE crossover freq.
tune procedures. Chart #9
except if L213, L215 are
changed.
NOTE: If C240 is found
defective, change to 2.7PF (VHF)/
2.4PF (UHF1)/2.4PF (UHF2)
*
RX
ONLY
TX
ONLY
NOTE: If C240 is found
defective, change to 2.7PF (VHF)/
2.4PF (UHF1)/2.4PF (UHF2)
*
NO
NO
NO
YES
YES
YES
YES
NO
NO
YES
YES
YES
YES
YES
YES
YES
YES
YES
TX
RX
NO NO
NO NO NO NO
NO NO
YES
**
MBEPF-23273-O
NO

Motorola MTX series Specifications

General

Brand	Motorola
Model	MTX series
Category	Portable Radio
Language	English