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Tuesday, 24 November 2009

Analysis of Short Flows in Nokia BB5 (part 2)


TAHVO Elimination
Disconnect the L2302, with these components removed, then the Vcore will be lost. Then check again, if the condition still the same? If so, it means there is no problem with Vcore for the RAP. When the heat was back to normal, then there are certain problems in RAPGSM (microprocessor).
Pull the L2301 and L2306, with these components removed, the input TAHVO from Vbatt will be lost. This led to a series of charging does not work. Check back, if the condition still the same? If so, it means there is no problem at TAHVO. If the heat back to normal, then it means there is a problem in TAHVO.
PA (Power Amplyfier) elimination
Pull Z7520, by depriving these components, Vbatt Voltage to the PA will be lost. Check back, if the current consumption to be normal, then there is a problem in PA.
RF IC (AHNE) elimination
Pull the L7502, with these components removed, the Vbatt voltage to the RF will be lost. If the current consumption to be normal, then there is a problem in the RF. If the flow remains high, then the problem is not found in RF. Replace the L7502.
Bluetooth IC elimination
Pull the L6077, with these components removed, the Vbatt voltage to the bluetooth IC will be lost. If the current consumption to be normal, then there is a problem in the bluetooth IC.
Camera IC and Regulator elimination
Pull L3303, if the flow becomes normal, then there is a problem in the camera or camera ICs. If the flow is still high, pull the L3304, if the flow becomes normal, then there is a problem in the camera regulator (N3300).
For the DSP on RAPGSM that obtain VIO voltage, the way to eliminate by pull RAPGSM. Then look the current reaction on Power Supply or feel if the RETU still hot? If it is back to normal, it means there is a problem in RAPGSM. If the RETU still hot, or power supply current is still high, it means the problem is not found in RAPGSM.
There are two possible short on RAPGSM, from foots of the RAPGSM or from RAPGSM module itself. If the short occurs on its feets, reball the IC. But if after reball still same, change the RAPGSM.
There are three short categories on mobile phones, namely :
  1. Short when the battery installed
  2. Short after pressing on/off switch
  3. Short when make a call
To overcome the condition number one, check and eliminate the components that obtain the voltage directly from Vbatt like PA, RETU, TAHVO, RF, etc.
To overcome the condition number two is more difficult. Check and eliminate the components that obtain the voltage from regulator like camera regulator, led regulator, etc.
The condition number three, the damage generally occurs in PA, because PA work when make a call or receiving a call.

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