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3 Static TX
3.1
Finding out if there is an amplitude or frequency fault
Open the phone and check for liquid damage.
No further action should be taken for a liquid damaged telephone.
Make sure the antenna connection X101 is not mechanically damaged, badly soldered or dirty
(varnish, glue, oxide...).
Give the board power, start the test program and connect the negative -4 V
Note! It is important that the negative -4 V
been started, the power amplifier might otherwise be damaged.
Measure the current consumption.
If the phone consume about 2 A, remember the current limit, is there most likely a short circuit
in the power amplifier, N401.
Confirm by measuring the resistance between N401 pin 14 and ground,
it should be larger than 5 Kohms but usually is around 200 ohms when N401 is faulty.
For GSM 900:
Start the transmitter in static mode on channel 62 and check the output power and frequency.
We propose following settings on the spectrum analyser while measuring CF- 902.4 MHz,
SPAN- 200 MHz, RBW- 10 kHz, VBW- 10 kHz and Sweep- 30 ms.
Check the frequency of the transmitter 902.4 MHz. If the frequency is misplaced, try to lower
the "Adjust sweep current" until the frequency of the transmitter has locked on.
If the transmitter does not have any output power at all or if it is very low, go to section 3.2.
If the transmitter does not lock on, go to section 3.3.
If the transmitter locks on, start it in switched mode on channel 62 with DAC 7 value at "FF".
Make sure the output power is 30 - 35 dBm, by using the spectrum analyser.
We propose following settings on the spectrum analyser while measuring:
CF- 902.4 HMS, SPAN- 0 MHz, RBW- 300 kHz, VBW- 100 kHz and Sweep- 0.8 ms.
If there is no switched output power at all or if it is too low, go to chapter "No serv".
If the output power is correct then the transmitter is without fault.
Test the phone again.
For GSM 1800:
Start the transmitter in static mode on channel 699 and check the output power and frequency.
We propose following settings on the spectrum analyser while measuring:
CF- 1747.6 MHz, SPAN- 200 MHz, RBW- 10 kHz, VBW- 10 kHz and Sweep- 30 ms.
Check the frequency of the transmitter 1747.6 MHz. If the frequency is misplaced, try to lower
the "Adjust sweep current" until the frequency of the transmitter has locked on.
If the transmitter does not have any output power at all or if it is very low, go to section 3.2.
If the transmitter does not lock on, go to section 3.3.
4/00021-3/FEA 209 544/18 B
Trouble Shooting Guide, Advanced
not is connected until after the test program has
DC
to P401.
DC
13(121)
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