Motorola MTM800 - PA Bias Failure Troubleshooting

9.1 - 12 TROUBLESHOOTING CHARTS: 450-470MHz
PA Bias Failure Troubleshooting
OK
Measure the DC current of the radio.
Use this as reference current.
Is the
DC current within
420-460mA
?
Check antenna switch
diodes D5451, D5551,
Q5551, Q5552,Q5804,
Q5802, JAVELIN
Check for 9.3V at U0150
pin 15 before replacing
U0150
DC at
U0150 pin 16
about 4.7V
?
Check for 9.3V at U0150
pin 15 before replacing
U0150
Send Tetra Com command
"PA_BIAS_M 1 xx" to set Bias 1 to xx.
Use a value from PA_BIAS_TBL_M 1
for xx.
Measure the DC current of the radio.
Can
the current
be set to 57-85 mA
higher than the reference
current by changing
Bias 1
?
Does
the DC change
at TP5402 if the
Bias 1 setting is
changed
?
Does
the DC change
at U0150 pin 4 if the
Bias 1 setting is
changed
?
Send Tetra Com command
"PA_BIAS_M 1 0".
Send Tetra Com command
"PA_BIAS_M 2 xx" to set Bias 2 to xx.
Use a value from
PA_BIAS_TBL_M 2 for xx.
Measure the DC current of the radio.
Check R5533, L5403,
L5502, 9V3_TX
before replacing
U5401
Check transistor stage Q5501
Can
the current
be set to 90-110 mA
higher than the reference
current by changing
Bias 2
?
Does
the DC
change at TP4409 if
the Bias 2 setting is
changed
?
Does the
DC change at
U0150 pin 18 if the
Bias 2 setting is
changed
?
Replace U0150
Send Tetra Com command
"PA_BIAS_M 2 0".
Send Tetra Com command
"PA_BIAS_M 3 xx" to set Bias 3 to xx.
Use a value from
PA_BIAS_TBL_M 3 for xx.
Measure the DC current of the radio.
Check
R5405, R5406, L5421
before replacing Q5421
Check transistor stage
Q5521
Can
the current
be set to 260-310 mA
higher than the reference
current by changing
Bias 3
?
Does the DC
change at TP5541 if
the Bias 3 setting is
changed
?
Does the
DC change at
U0150 pin 24 if the
Bias 3 setting
is changed
?
Replace U0150
Check
R5431, L5431, L5503
before replacing Q5431
Check transistor stage
Q5542
Yes
Yes
Yes
Yes
Yes
Yes
YesYes
Yes
Yes
Yes
No
No
No
No
No
No No
No
NoNo
No
Failure:
PATS parameters PA_BIAS, BIAS1-3_CUR, BIAS_1-3_SP failed
Tetra Com Script for PA Bias Test
TEST_ENTER
DELAY 18
Check for "Radio HW is READY"
MODE IDLE
INTR DIS
FREQ RX 380.075
L1TIMER ON
TXPOW 1
RFTON ATT 0
RFTON FRQ 10
RFTON CHN IQ
PA OFF
PA_BIAS_M 1 0
PA_BIAS_M 2 0
PA_BIAS_M 3 0
PA_BIAS_TBL_M 1
PA_BIAS_TBL_M 2
PA_BIAS_TBL_M 3
MODE RFTONE
Use MODE IDLE to terminate
RFTONE mode
Connect the radio's accessory connector to the Tetra Com
interface.
Connect the radio's antenna connector to the
high power RF output on the IFR.
Run Tetra Com script for PA Bias Test
Measure DC levels with a multimeter.
Measure the DC current of the radio
If the cover is removed from the chassis, the RF PA is
disabled to prevent overheating of the FET devices.
To measure the power at the antenna connector, the
pressure pad can be used to short the contact area on the
main board. This should be done only for a few seconds.
Start
6866539D31.book Page 12 Tuesday, March 20, 2007 6:32 PM