Motorola MTM800 - RF Power Amplifier Troubleshooting

TROUBLESHOOTING CHARTS: 450-470MHz 9.1 - 11
RF Power Amplifier Troubleshooting
Measure the output power
at the antenna connector
Check
R5453, R5454, R5455,
R5451, R5452, C5451
Replace L5812
Tune Radio
RF Power at antenna
connector
?
RF level
at TP5451 about
300mV
?
Are both
splitter outputs
measured at C5862
and C5863 about
300mV
?
Replace U5803
Is
DC current
greater than
850mA
?
PA bias problem!
Go to PA Bias Tuning Chart
RF
level at
TP5451 about
300mV
?
Check D5451, D5551 and their DC
path, check components between
C5452 and antenna connector.
RF
level at
TP5401 about
220mV
?
No JAVELIN output signal
Go to JAVELIN Chart
RF
level at
Gate of Q5421 about
160mV
?
DC
at TP5402 about
4.4V
?
PA bias problem!
Go to PA Bias Tuning Chart
Check R5533, L5403, 9.3V DC at R5533.
Check components between TP5401 and
Q5421 before replacing U5401
RF level
at Q5421 Drain
about 2.2V
?
DC
at TP4409 about
2.2V
?
PA bias problem!
Go to PA Bias Tuning Chart
Check components
between
Q5431 and D5451
Check L5431, components between
Q5421 and Q5431, check 13.2V DC
at L5431 before replacing Q5431
DC
at TP5541 about
2.2V
?
RF level
at Q5431 Drain
about 7V
?
Check L5421 and 9.3V DC at
L5421 before replacing Q5421
PA bias problem!
Go to PA Bias Tuning Chart
Failure:
No or low RF output power.
Too high RF output power.
PATS parameters ADJ_PWR1-5, ATT_SP1-5,
DC_CUR1-5, TX_PWR_F1-5 failed.
Tetra Com Script for TX Power Test
TEST_ENTER
DELAY 18
Check for "Radio HW is READY"
MODE IDLE
INTR EN
FREQ TX 429.925
L1TIMER ON
TXPOW 6
MODE TXNDC
Use MODE IDLE to terminate transmit mode
Connect the radio's accessory connector to the Tetra Com
interface. Connect the radio's antenna connector to the
high power RF input on the IFR.
Setup IFR:
Select high power input
No System,
TX Test,
TX Frequency 429.925MHz
Spectrum Analyser
Set Reference Level to 40dBm
Run Tetra Com script for TX Power Test
Measure RF levels with the high impedance RF probe and
millivoltmeter.
Measure DC levels with a multimeter.
No
No
No
No
No
No
No
No
No
No
No
Yes
34 - 37dBm
> 37dBm
< 34 dBm
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Start
6866539D31.book Page 11 Tuesday, March 20, 2007 6:32 PM