Pa Bias Failure Troubleshooting - Motorola MTM800 User Manual

9.1 - 12

PA Bias Failure Troubleshooting

Failure:
PATS parameters PA_BIAS, BIAS1-3_CUR, BIAS_1-3_SP failed
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.
Measure the DC current of the radio.
Use this as reference current.
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.
higher than the reference
current by changing
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.
higher than the reference
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.
be set to 260-310 mA
higher than the reference
current by changing
Start
No
Is the
Check antenna switch
DC current within
diodes D5451, D5551,
420-460mA
Q5551, Q5552,Q5804,
?
Q5802, JAVELIN
Yes
Can
No
the current
the DC change
be set to 57-85 mA
at TP5402 if the
Bias 1 setting is
Bias 1
?
Yes
Yes
Check R5533, L5403,
L5502, 9V3_TX
before replacing
U5401
Can
the current
No
be set to 90-110 mA
change at TP4409 if
the Bias 2 setting is
current by changing
Bias 2
?
Yes
Yes
Check
R5405, R5406, L5421
before replacing Q5421
Can
No
the current
Does the DC
change at TP5541 if
the Bias 3 setting is
Bias 3
?
Yes
Yes
Check
R5431, L5431, L5503
OK
before replacing Q5431
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
Check for 9.3V at U0150
pin 15 before replacing
U0150
Yes
DC at
U0150 pin 16
about 4.7V
?
Does
Does
No
the DC change
at U0150 pin 4 if the
Bias 1 setting is
changed
changed
?
?
Yes
Check transistor stage Q5501
Does
Does the
No
the DC
DC change at
U0150 pin 18 if the
Bias 2 setting is
changed
changed
?
Yes
Check transistor stage
Q5521
Does the
No
DC change at
U0150 pin 24 if the
Bias 3 setting
changed
is changed
?
?
Yes
Check transistor stage
Q5542
TROUBLESHOOTING CHARTS: 450-470MHz
No
Check for 9.3V at U0150
pin 15 before replacing
U0150
No
No
Replace U0150
?
No
Replace U0150