Open Loop Power Test - Motorola MTH500 Service Manual

Troubleshooting
Measure the
Open Loop power
by using PATS
Is the
output power
less than
120mW (20.8dBm)?
Yes
Are voltages
2.775V_RF, 5V_RF,
RAW_B+_RF and 2.5V_TX
supplied to the Transmitter
components?
Yes
Is there
~ 2.5Vdc of ANT_EN
signal on Q806 pin
(or C830) during
Tx slot?
No
Using a Power Probe, measure
RF power at the RF PA
U809 input (pin 6).
Is power < -20 dBm?
Yes
Using a Power Probe,
measure RF power at the
LNODCT U803 outputs
(pins 51,52).
A
3 - 16

Open Loop Power Test

This test should be carried out only after the successful completion of the previous tests.
Is the
output power
No
above 0.5W (27dBm) ?
No
OK
Check the battery,
regulators Q800, Q805,
Q806, Q807, Q911,
elements on 2.5V_TX lines.
No
Replace if faulty.
Perform the Open loop
power test again.
Check E810.
Yes
Perform REDCAP2 test.
Repeat Open Loop
Power Test.
Using a Power Probe test TX
line-up (starting from RF
PA U809 output: pins 12,13)
by measuring output power
after every component of
Transmitter till Antenna.
No
It should be as specified
in the spread sheet, otherwise
replace the damaged
components.
Perform the Open loop power
test again.
Yes
Is the radio
in oscillation?
Yes
Check RF PA U809, Isolator FL801, Coupler U806,
components: E801, E808, E809, L916, L917, L920, L921,
L923, L918, L919, C1030,C1028,C1029, C822,C867.
Replace damaged parts.
Perform the Open loop power test again.
Check the bias voltages
on pins 8,16 of RF PA U809.
Check resistors R827
and R828, regulators Q807
and Q911, replace parts
if faulty.
No
Perform the Open loop
power test again
68P02963C70-O