(Closed Architecture Controller) - Motorola Handie-Talkie MTX Series Theory/Troubleshooting Manual

EMER
Enable and
press EMER.
Button. Red LED
does not blink.
NO
PTT
OK?
See PTT
Troubleshooting
YES
Press
YES
EMER
Button
U705 pin 62
low?
NO
Check
J703-18
Voltage.
EMER. SW
Enable and
Press RAT.
RAT
LED does not
Blink
Turn channel
Radio
switch sequence
CHANNEL Info. with
RX freq. not as
SW
program.
Correct
NO
Flip the toggle
3-POSITION switch. Radio not
SW function as
programmed.
Radio could
EXT
not PTT
PTT
externally.
Radio has no
EXT
ext. audio
SPK
Enable low
LOW
battery alert.
BATTERY Alert at nominal
battery voltage.
Switch to PL Mode
PL & MDC
and MDC SEL CALL
SIGNALLING
option enabled.
Pulse train at
U705 pin 6
?
NO
48
TROUBLESHOOTING FLOW CHART #8A

(Closed Architecture Controller)

PTT MONITOR
Press PTT. Press MON.
Red LED Button, Radio
does not does not
light up. respond.
Press PTT,
NO
Press MON
U705 Pin 61
Button U705
Low?
pin 59 low
?
Check U703-1
Voltage PTT
YES
NO
SW
Check
PTT J703-2
YES
Voltage
J704-4
HIGH? MON. SW
NO
LED U704
See FGU
R719
Troubleshooting
OK
Chart #4A
?
NO
YES Enable &
Can
NO
Press RAT
radio
Button.
key up
U705 pin 65
?
low?
NO
YES
Go to PTT
U705 pins Check
YES
NO
40, 41, J703-12, 13,
42, 43 14, 15 voltage
RSS
status as chan. SW
Table 1?
?
YES
Reprogram
Check
U705 pin 50
J710, R711
NO
POSA = 0V
J703-7voltage
POSB = 2.5V
mode SW.
POSC = 5V
?
YES
Check
Ext
NO
J701-10, 18
PTT U705
voltage
Pin 37, 38
ext. mic.
low
?
YES
Check
U705 NO
J01-10, 18
pin 38 = low
voltage
pin 37 = high
ext. spk.
?
YES
Read
YES
U705
radio
low batt. pin
48 > 3.8
threshold
info. ok? ?
NO NO
Reprogram
Check R708,
the correct
R709, C730
threshold
voltage.
YES YES
Pulse
MCU is
train
OK
appear at
U705 pin 9
?
NO
Radio Button
Closed Controller
functions and
Check
Signalling
Problems.
Power Up
YES
Alert Tone
OK?
Note 1.
YES
U705
Pin 77
EXTAL =
7.9488 MHz
?
Speaker
NO
OK
?
NO
U701
Pin 33 =
2.1/2.4
YES
MHz
YES
Replace
Speaker
YES
Replace
Faulty
Component
5V at
U709
Pin 1
?
Check
J703-3
voltage
RAT SW
YES
U705
pin 79
High
?
YES
5V at
collector
Q702
?
YES
U705 pin
80 MOD _B
high
?
YES
U705 pin
81 MOD _A
High?
YES
OFF Radio
& Power Up.
Any data on
U705
pin 83?
YES
YES
Change
U701
NOTE 1: If Power Alert is Enabled:
300Hz Tone - Micro-P Fail Self Test
300Hz Tone - Micro-P Fail Self Test
900Hz Tone - Micro-P Pass Self Test
No Tone - Micro-P is not running normally.
NOTE 2: Wrong Codeplug Data could cause radio failure.
Replace
U705
Not able to
Before replacing
program RF
MCU, check MCU
YES
Board ICs
voltages and check
for I/O activities.
YES NO
Read Check setup and
Radio check J701,
OK? voltages at pins
22, 26.
YES
Check
NO See FGU
NO
J704
Troubleshooting
Pin 13 =
Chart #4A
2.1/2.4
MHz
YES
NO 7.5V at NO
Check Vol
U709
SW, Fuse and
Pin 8
Battery.
?
YES
Check R717
NO
pin 5 of U709
pin 24 of U701
C708
NO
YES
6.8V at
Replace
base of
Q702
Q702
?
NO
Replace
Q705
NO
Check
R731
NO
Check
R730
NO
U701
pin 35 =
3.6864 MHz
CHANNEL PIN
YES
?
1
NO
2
3
4
Replace
5
U701
6
7
8
9
10
11
Replace
12
U705
13
14
15
16
Reprogram the
correct data.
Note 2.
Check
C774
Replace
U709
Table 1
PIN PIN PIN
40 41 42 43
1 1 1 1
1 1 1 0
1 1 0 1
1 1 0 0
1 0 1 1
1 0 1 0
1 0 0 1
1 0 0 0
0 1 1 1
0 1 1 0
0 1 0 1
0 1 0 0
0 0 1 1
0 0 1 0
0 0 0 1
0 0 0 0
MAEPF-23278-O