Motorola T720 - Transmitter Troubleshooting

63 © 2002 Motorola, Inc.
Product Support Tools T720
RECEIVER TROUBLESHOOTING
TRANSMITTER TROUBLESHOOTING
Check for I and Q going into RFT3100.
Check for LO input into RFT3100. Level
should be about –15dBm.
Check for Tx IF VCO Frequency and
control voltage.
Tx IF VCO frequency is 457.2MHz for
800MHz CDMA and AMPS, and
527.2MHz for PCS CDMA.
Control voltage at 457.2MHz is about
1volt, and 2volts at 527.2MHz.
Check for Tx IF (near the Tx IF Filter)
Tx IF is 228.6MHz for 800 MHz CDMA
& AMPS
Tx IF is 263.6MHz for 1900 MHz CDMA
Check for Tx RF at RF filter input and at
PA input.
n No Service
n
Make sure phone has service programming and has phasing data stored. This can be verified with
QPST.
n
Check for Rx IF VCO (367.2MHz) to be on frequency. Measure Rx IF VCO control voltage. It should
be between 1 and 2 volts.
n Check for RF signals after each of the filters, and major functional blocks.
n Check for RF at Antenna -> Diplexor -> Duplexor -> LNA -> RF Interstage
Filter -> Mixer -> IF.
n Check LO frequency is locked and is present at the input of the mixer (RFR3300).
n Check supplies to each functional block. Receiver runs off 2.75V.