Motorola MTP700 Detailed Service Manual page 115

TRANSCEIVER 400 MHz
Open Loop Power Test
This test should be carried out only after the successful completion of the previous tests.
Measure the Open
Loop Power by
using PATS.
Is the output
power less than
28dBm?
Yes
Is the output
Are voltages V4_2.775V,
5V_RF, SWB+ and RAW_B+
supplied to the transmitter
components?
Yes
Is there -2.5Vdc of
ANT_EN signal on Q5001
pin (or C5007) during TX
slot?
No
Using a Power Probe, measure
RF power at the ldmos driver
U4001 input (pin 16).
Is power <-5dBm?
Yes
Using a Power Probe, measure
RF power at the LNODCT
U6002 outputs (pins 51, 52).
MTP700 Portable Radio / Detailed Service Manual
No Is the output
power above
31dBm?
No
Check the supply switches
and regulators Q4100,
Q6002, U4002, Q5001,
No
U4102 for functionality.
Replace if faulty.
Perform the Open Loop
Power test again.
Check L5005. Perform
Yes
REDCAP2 test.
Repeat Open Loop
Power test.
Using a Power Probe test TX line up
(starting from RF ldmos driver U4001
output: pins 6, 7) by measuring output
power after every component of
No
Transmitter till Antenna.
It should be as specified in the spread
sheet, otherwise replace the damaged
components.
Perform the Open Loop Power test again.
A
Yes
Is the radio in
oscillation?
Yes
Check RF PA U4001, Q4001.
Isolator FL5001, Coupler U5001 and
the components in their supply lines.
Check the bias voltages on
pin 16 of U4001 and pin 7 of
No
U4102. Check L4003, C4001,
R4006 and R4004, R4005,
C4018, C4027, R4007.
Perform the Open Loop
Power test again.
4.1 - 81