Dc Supply Troubleshooting - Motorola MTM800 User Manual

9.1 - 6

DC Supply Troubleshooting

Short accessory connector pins 10 and 9 to switch on the radio.
Before replacing U0301, check
for 13.2V at U0301 pin 4 and
check R0307, R0308
Failure:
No TX DC supply.
9.3V supply (9V3) ok
Failure:
No 9.3V DC supply.
No Digital DC supply.
Start
0V DC at
U0301 pin 2
?
Yes
No
9.3V DC at
U0301 pin 5
?
Yes
5V DC at
U0303 pin 3
?
No
Before replacing U0303, check
for 9.3V at U0303 pin 1
Start
No
9.3V DC at
Before replacing U0300 check for
U0300 pin 5 13.2V at pin 4, 0V at pin 2 and check
?
resistors R0305, R0306
Yes
No
2.8V DC at
Before replacing U0307 check for
C0324
9.3V at C0308
?
Yes
No
5V DC at
Before replacing U0304 check for
U0304 pin 1
9.3V at pin 8
(TP 0301)
?
Yes
TX DC supply ok
TROUBLESHOOTING CHARTS: 450-470MHz
No
Yes
13.2V DC
at Base of
Q0303
?
No
Yes
0V DC
at Collector of
Q0302
?
No
Yes
0.7V DC
at Base of
Q0302
?
No
Before replacing Q0302 check
components between Q0302
Base and accessory connector
pin 10
Replace
Q0303
Replace
Q0301
Replace
Q0302
Failure:
No EXT SW B+ DC supply.
9.3V supply ok
Start
Before replacing U0302 check for
13.2V at pin 4, 0V at pin 2 and check
resistors R0303, R0304