Motorola APX 5000 Service Manual page 165

Troubleshooting Charts: PA Failure
PA Failure – Page 4 (Multi Switch)
Is resistance
greater than 20K
Ohms?
Yes
No
Remove ferrite bead E1101
to disable the PA's .
In TX mode, measure
resistance on U1102 from
pin 3 to pin 28.
Check pins 2, 3
Is resistance
No
and 4 for solder
less than 10
Ohms?
Yes
Verify voltage
No
Is the pin
divider at R1183
and R1184 under shorted?
sheild SH12.
Clear short, or
replace U1102.
TX
RX
4
Lift shield SH12 and
check switch U1102
for functionality.
In RX mode, measure
resistance on U1102
from pin 9 to pin 28.
Is resistance
No
less than 10
Ohms?
Yes
In RX mode, measure
resistance on U1102
from pin 3 to 28 and
from pin 22 to 28.
Check pins 2,
3, 4, 21, 22, 23,
Are any of the
27, 28 and 29
pins shorted?
for solder shorts.
Yes
Clear short, or
replace U1102.
shorts.
Are any of the
pins shorted?
Clear short, or
replace U1102.
Check pin 12
No
for solder
shorts.
Yes
Verify logic to pin 13, 14 and
15 of U1102, using the table
to the left for reference. Logic
high ~ 3 V, and logic low ~ 0 V.
Pin
13 14 15
0 1 1
1 0 0
shorts on the RF pins
Check pins 8,
Are any of the
9, 27, 28 and
29 for solder pins shorted?
shorts.
Yes
Clear short, or
replace U1102.
No
In TX mode, measure
No
resistance on U1102
from pin 22 to pin 28.
Yes
Is resistance
less than 10
Ohms?
In either TX mode,
measure resistance
on U1102 from pin 9
to 28.
Is resistance
greater than 20K
Ohms?
Were all
Is supply to
No
U1102 pin 12
resistances
near 3.3 V?
correct?
Yes
Check pins 13, 14
No
Is logic correct?
and 15 for solder
shorts.
Yes
Check for solder
1,2,23,24, and 28.
If all else is OK, and
resistance is still high,
Were any pins No
then replace U1102
shorted?
and re-measure
power.
Yes
Clear short, or
replace U1102.
No
Check pins 21,
No
22 and 23 for
solder shorts.
Yes
Check pins 8,
No
9, 27, 28 and
29 for solder
shorts.
Yes
U1102 is functional,
Yes
follow PA specific
charts.
This logic is controlled by several
IC's that cannot be probed
because of the package type.
Check U1116, U1117, U1118,
No
Are the pins
and U1123 for any issues and
shorted?
replace as necessary. If no
trouble found see FGU trouble
Yes
shooting charts for further TX
signaling information.
Clear short, or
replace U1102.
5-59
No
Are any of the
pins shorted?
Yes
Clear short, or
replace U1102.
No
Are any of the
pins shorted?
Yes
Clear short, or
replace U1102.