User Guide

PAMS
Technical Documentation
NHD–4
Disassembly & Troubleshooting
Page 42
Original 11/97
•Check the SWAGC line at R830, should be logic level low, approx .0 V.
If not, confirm that the phone is in the CDMA Troubleshooting Mode. Ensure VRXM
is at about 4.40 V at R832. Inspect V708, R765 and R830. Ohm out line from R765
to the ASIC N704 pin 94.
•Check the RX_CAL line at R783. It should be logic level high, near 2.75 V.
If not, confirm that the phone is in the CDMA Troubleshooting Mode. Ensure VRXM
is at about 4.40 V at R832. Inspect V1, V708, R6, R765, R783, and R785. Ohm out
the RX_CAL line from pin 114 of the ASIC N704 to R785.
Chart of CDMA RX DC Node Voltages
The following chart summarizes the node voltages of the CDMA RX when
the phone is in the CDMA RX/TX Mode with a 881.62 MHz signal input of
–65 dBm, CW.
Node Voltage
(V)
BFILCT2 IC (N2), pin 4
3.10
BFILCT2 IC (N2), pin 8
3.05
CDAGCR IC (N1), pin 13
4.40
R17 – voltage drop across this resistor
0.33
R16 – voltage drop across this resistor
0.037
V7 – collector of CDMA IF LNA, pin 1
1.33
V7 – base of CDMA IF LNA, pin 3
1.38
V7 – emitter of CDMA IF LNA, pins 2, 4
0.60
V9 – collector of 1st IF amp, pin 1
3.50
V9 – base of 1st IF amp, pin 3
1.85
V9 – emitter of 1st IF amp, pins 2, 4
1.12
V12 – collector of LNA
3.90
V12 – base of LNA
1.00
RF Gain Switches N701 and N702. Pin 1
3.80
RF Gain Switches N701 and N702. Pin 8
0.00
SWAGC line at R830
0.00
RX_CAL line at R783
2.75
Baseband Demodulation Check
If you have an oscilloscope available you may use it to do a visual check
on the demodulated baseband CDMA I or Q signal . With the phone
tuned to channel 384, feed a –75 dBm, 881.62 MHz unmodulated CW RF
signal into the receiver. Initiate the CDMA Troubleshooting Mode from
Service Software. Use a standard scope probe at C58, the RX_I signal.
It should appear as a fuzzy sine wave of approximately 190 mVpp. This
frequency will be approximately 100 kHz.