Transmitter; General Instructions For Tx Troubleshooting - Nokia NSW-6 Series Disassembly & Troubleshooting Instructions

NSW-6
Disassembly & Troubleshooting

Transmitter

General Instructions for TX Troubleshooting

Always use RF–cable connected from antenna interface to analyzer
through an attenuator. This is important to protect analyzer against exces-
sive rf–power and not to let any unwanted RF power leak to the cellular
frequencies.
Start the Wintesla software and select TX mode under testing
(AMPS,DAMPS or TDMA1900). It is useful to select mid channel (383 for
AMPS/DAMPS or 1000 for TDMA1900) and power level 2. Select random
data for digital mode of operation.
One of the basic test is to monitor current when transmitter is on. If cur-
rent consumption does not change when transmitter is set on the fault is
in the PA area.
Nominal current consumptions on power level 2 in mid channel:
AMPS:
TDMA800:
TDMA1900:
Also, if pressing the PA package more tightly to PCB does have an effect
on current consumption the fault is in the PA. In case of a faulty PA, the
replacement should be done only under correct ESD precaution and us-
ing a hot air gun set to 10m/s and 300 degrees centigrade. The new PA
must be taken from a vacuum package and the heating process should
be done in less than 30 seconds. Note, that the ground slug of the pack-
age must be properly soldered and excessive solder material, if any, has
to be removed.
If any components in the TX chain are replaced, the power level tun-
ings have to be checked and retuned.
Tuning targets are presented at next page.
Set power supply voltage.
Connect pulse power meter or spectrum analyzer. Use attenuator, if
needed.
Set settings for spectrum analyzer in power level tuning:
Page 32
650–850 mA
300–350 mA
350–400 mA
Set span 0 Hz
Set Ref LVL 30 dB
Set Ref LVL offset and ––> Attenuation to Antenna Pad
Set RBW and VBW 300 kHz
Set sweep time 50 ms
Set TRIG: SWEEP CONT, VIDEO –10 dBm
E Nokia Mobile Phones Ltd.
PAMS Technical Documentation
Issue 1 12/99