Ericsson T28S Troubleshooting Manual page 12

3.5 Consumes less than 15 mA
3.5.1 Consumes no current
Open the phone and check for liquid damage.
Make sure X100 is not dirty, damaged or incorrectly soldered.
Replace the dome foil.
Power up the board.
Measure the VBATT voltage on C400, at the pin close to C401 (3.70 V).
If the voltage is incorrect, replace X100.
If the voltage at C400 is correct, measure the voltage at pin 2 of V610 (3.65 ± 0.10 V).
If the voltage at pin 2 of V610 is correct, replace V610.
If the voltage at pin 2 of V610 is incorrect, send the unit on according to the local company
directives.
If the fault remains, send the unit on according to the local company directives.
3.5.2 Consumes less than 15 mA
Open the phone and check for liquid damage.
Power up the board and start it by pressing On/Off key.
Measure the VDIG voltage on C703, at the pin close to C834 (2.75 V).
If the voltage is incorrect, check that the resistance from C703, the pin close to C834, to
ground is more than 40 kohms.
If the resistance is correct send the unit on according to the local company directives.
If the resistance from C703 is incorrect, replace C703.
Measure the CORE voltage on C702, at the pin close to R701 (2.50 V).
If the voltage is incorrect measure the resistance from C702, the pin close to R701, to ground.
It should be more than 200 kohms.
If the resistance is correct send the unit on according to the local company directives.
If the resistance from C702 is incorrect, replace C702.
If VDIG and VCORE are correct measure the VDSP voltage (1.80 V) at N740 pin 5.
If the voltage is incorrect, replace N740.
If VDSP is incorrect after the replacement of N740, measure the resistance over C740 (>20
kohms) and R705 (0 ohm). Replace if incorrect.
If both the resistances are correct, send the unit on according to the local company directives.
If VDSP is incorrect after replacement of C740, replace D900.
If the fault remains, send the unit on according to the local company directives.
4/00021-2/FEA 209 544/19 E
Trouble Shooting Guide, Standard
12(29)