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PF768, Standard Electrical Repairs
If the fault remains, send the phone to the next level.
8.3 The background illumination for the display
is missing or faintly glowing.
Open the phone and check for liquid damages.
Make sure all the LEDs (H651-H654, all of class A, fig. 8.1) are mounted and cor-
rectly soldered.
Give the board power and start it up by pressing the On/Off key (in the fixture or in
the back cover with a dummy battery inserted, mount system connector to make the
board lie steady in the back cover).
• If a few but not all of the LEDs aren't lit, replace them.
• If none of the LEDs are lit, measure the resistance of one of them.
* If the resistance is ~0 ohms there's a short circuit in at least one of the
LEDs. Remove them one at a time and measure the resistance after every
LED removed. When the resistance increases the faulty LED has been
removed.
* If the resistance of the LEDs is high, make sure there's VBATT voltage at
the marked side of the LEDs (fig. 8.1).
* If VBATT voltage is missing it's likely due to liquid damage and the
phone is to be discarded.
* If the VBATT voltage is correct, check that R612 (~0 ohms, class A),
R610 (~33 ohms, class A) and R611 (~0 ohms, class A, all in fig. 8.4) are
mounted and of the correct resistance.
Fig. 8.4
4/00021-2/FEA 209 544/11.C
45
(68)
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