Ericsson SH 888 Trouble-Shooting Instruction page 39

9.3 Background illumination fault
Open the phone and check for liquid damages. Make sure all the LEDs, H651-H660
(class A, fig. 9.3), are mounted and properly soldered.
Give the board power and start it up. If only a few of a group, H651-H654 (display
illumination) or H655-H660 (keyboard illumination), aren't lit, replace them.
If H655 and H656 aren't lit, measure the resistance of R659 (33 ohms, class A, fig.
9.3).
If all of the LEDs in only one group (display illumination or keyboard illumination)
aren't lit, measure the resistance of a LED in that group (anyone, they're parallel).
• If it's less than 1 Mohms, remove a LED at a time until the problem is solved.
• If it's more than 1 Mohms, measure the resistance of:
- R610 (47 ohms, class A, fig. 9.3) for H655-H660. If it's ok, replace V614 (class
A, fig. 9.3).
- R660 (0 ohms, class A, fig. 9.3) and R609 (27 ohms, class A, fig. 9.3) for
H651-H654. If they are correct, replace V613 (class A, fig. 9.3).
If none of the LEDs are lit, measure VBATT at one of the LEDs, H651-H660.
Measure both sides. It should be 4.8V at the VBATT side.
• If there is no VBATT at the LEDs, check at the VBATT connector (fig 9.1).
* If there is no VBATT there either, proceed to chapter 3 ("Doesn´t start"-
fault).
* If there is VBATT, measure the resistance from VBATT to the VBATT side
of the LEDs (~0 ohms). If it's incorrect there's a foil damage and the phone is
to be discarded.
4/00021-2/FEA 209 544/3.D
SH888, S868, Standare Electrical Repair
Fig. 9.3
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