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Trouble Shooting Guide, Advanced
14.3 How to find the fault
The fault can be in either the current measuring or the logical part/the AD-transforming.
You can find out which part is broken by measuring IMEAS and ICONT.
Start the board in the test program.
Set the battery voltage at +4.8 V
.
DC
Set DCIO at +8.7 V
, but do not connect the DCIO-voltage to the phone.
DC
Measure IMEAS on N450 pin 5 zero V
.
DC
Go to Logic \ Logic/SIM.
Set ICTRL high by pressing ICTRL.
Measure IMEAS again +0.5 V
.
DC
Turn off ICTRL.
If the voltage is incorrect, the fault depends on R421, VRAD or N450.
Connect DCIO to the system connector.
Set ICTRL high.
Measure IMEAS; it will change from +0.5 V
to +1.9V V
.
DC
DC
Set ICTRL low.
If the voltage IMEAS is too high, the fault usually depends on R421 or N450, but sometimes
also N800.
If the voltage IMEAS is too low, measure the resistance of R411 390 ohms.
If the resistance is lower, it usually depends on a short circuit in V401.
If the resistance is correct, start the board in the test program and check VRAD.
If VRAD is too low, the fault probably is due to N450, N412 or a short circuit in one of the
components fed by VRAD.
If VRAD is correct set ICTRL high again and measure the voltage on V401 pin 4 zero V
.
DC
If the voltage on V401 pin 4 is too high, measure ICONT on N450 pin 1 +3.4 V
.
DC
If ICONT is missing, the fault is probably due to D600 or C637.
If ICONT is correct but the voltage on V401 pin 4 is incorrect, the fault is due to N450.
If IMEAS and ICONT are correct, the fault is in the AD-transforming, but first measure the
resistance between AGND- X602: 4 and GND- X602: 10 zero ohm.
If the resistance is too high, there is a foil damage and the board has to be discarded.
If the resistance is correct, the fault usually depends on the feed voltage VANA, VDIG or N800,
but sometime on D600.
4/00021-3/FEA 209 544/18 B
62(121)
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