Ericsson I 888 Trouble-Shooting Instruction page 12

I888, Standard Electrical Repairs
replace the corresponding regulator (fig 3.1, all are class A). If the resistance is too
low, send the phone to the next repair level.
C720
VBATT
3
4
2
N706
1
5
R719
1
V702
3
2
R720 C720:+
V711
Fig. 3.2
Check the amplitude on the "clock" B510:1 (~1v t-t, class C, fig 3.1). Measure the
amplitude using an oscilloscope, spectrum analyzer, frequenzy counter, diode
prob... Ifthe amplitude is too low, send the phone to the next repair level. Check the
solderings on D600 or D610 (fig 3.1). If they are fine and it is sure B510 is okay,
then replace D600 (class B) and D610 (class A). Try to programe it in the flash pro-
grammer between each exchange.
3.4.2 Can be programmed, but doesn´t start afterwards
or is troublesome during programming.
Open the phone and check for liquid damages. Make sure the system connector pads
are not damaged or burned. Measure the resistance of R421 (0,1 Ohm, class B, fig
3.1). After every repair of the charging function, you have to verify the function
using the method mentioned in section 6.1.1. Attach the board to the fixture. Keep
it powered up with DCIO high. Check VDIG and VDSP (3.2 V, fig 3.1). If any of
the voltages are too low, measure the resistance to ground (VDIG >500 Ohm, VDSP
>25 kOhm). If the resistance is correct, replace the corresponding circuit (VDIG -
N702 (class A) and VDSP - N701 (class A)). If the resistance is too low, send the
phone to the next repair level. If any of the voltages are too high, replace the corre-
sponding circuit. Check Powerreset (PWRRST) at C710 (>3 V, Fig 3.1). If it is
lower, measure the resistance of R725 (100 kOhm, class A, fig 3.1). If it is correct,
replace C710 and N703, (both are class A, fig 3.1). Measure the voltages on
VRAD, VVCO and VRPAD (3.8 V, fig 3.1). If one or more of the voltages are
oncorrect, measure the resistance to ground (>50 kOhm). If the resistance is correct,
replace the corresponding regulator (fig 3.1, all are class A) . If the resistance is too
low, send the phone to the next repair level. Check the solderings on D600 or D610
(fig 3.1). If they are fine, replace D610 (class A) and D600 (class B). Try to program
the phone in the flash programmer between each exchange.
12
(42)
4-00021-2/FEA 209 544/5.C