Pa Bias Failure - Motorola MTM700 Detailed Service Manual

9.2 - 12
PA Bias Failure Troubleshooting
Failure:
PATS parameters PA_BIAS, BIAS1-3_CUR, BIAS1-3_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.
MTM700 Mobile Radio / Detailed Service Manual TROUBLESHOOTING CHARTS (800MHz)
START
YES
Is the voltage at
Is current for
C5871 @ 5V?
Bias 1 0?
Does the voltage at
TP5402 increase
when Bias 1 is in-
creased?
YES
Does the voltage at
Is current for
TP4402 increase
Bias 2 0?
when Bias 1 is in-
NO
YES
Does the voltage at
Is current for
TP5541 increase
Bias 3 0?
when Bias 1 is in-
NO
Replace U0150
5V_TX_SW is not present.
Check Q5804 and Q5802.
NO
Check Bias components for
Q5804 and Q5802. Check
that voltage on Pin 11 of
ADDAG U5802 is <0.2V.
YES
NO
Check U5501 and its bias components.
Check 9V_TX_SW at C5551, Q5551, and
YES
Check bias components for U5401. If
NO
Check Q5521 and its bias components.
creased?
YES
Check bias components for Q5421.
If OK, replace Q5421.
NO
Check Q5542 and its bias components.
creased?
YES
Check bias components for Q5431. If OK,
YES
Problem Fixed
Tetra Com Script for PA Bias Test:
TEST_ENTER
DELAY 10
Check for "Radio HW is READY"
MODE IDLE
INTR DIS
FREQ TX 806.075
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
OK, replace U5401.
replace Q5431.
Still does not
bias tune?
NO