User Guide

PAMS
Technical Documentation
NHD–4
Disassembly & Troubleshooting
Page 32
Original 11/97
Testing CDMA TX Gain Limiting
To test the CDMA TX Gain Limiting control perform the following steps:
1. Place the phone in the CDMA Troubleshooting Mode.
2. With an oscilloscope probe the LIM_ADJ line at C807.
3. Adjust the gain of the CDMA transmitter using the CDMA TX manual
gain control mechanism found in the Service Software.
4. The LIM_ADJ line will remain at about 3.2 VDC until the TX output
power reaches its limit, approximately 24 dBm. At this point the LIM_ADJ
line will toggle continuously, appearing as a square wave 3.2 Vpp with an
approximate frequency of 400 Hz.
Testing Dynamic TXB
To test the Dynamic TXB functionality, perform the following steps:
1. Place the phone in the CDMA Troubleshooting Mode.
2. Use the Service Software CDMA TX manual gain controls to achieve
10 dBm CDMA TX output power.
3 .Read the total current draw of the phone. It should be approximately
530 mA.
4. Increase the CDMA TX output power to 23 dBm. The current draw
should rise to approximately 690 mA.
Note the difference is about 150 mA, which is the difference between the two current
biasing levels.
CDMA TX
10 dBm
(mA)
CDMA TX
23 dBm
(mA)
AMPS Power
Level 7
(mA)
AMPS Power
Level 2
(mA)
Current Draw 530 690 400 610
Testing CDAGCT IC (N100) Gain Control
To test the gain control abilities of the CDAGCT IC (N100) do the
following:
1. Place the phone in the CDMA Troubleshooting Mode
2. Observe the TX output with a spectrum analyzer or CDMA test set. Be
sure to read bandpower over a 1.23 MHz band.
3. Use the CDMA TX manual gain control found in the Service Software
to adjust the output power from its minimum (noise floor) to 15 dBm.
4. Observe the TX_Gain voltage at C213 and the TX_ICT current as a
voltage drop across R116. The table below details approximate values
that should be read.