Ericsson PF 768 Troubleshooting Instructions page 46

PF768, Standard Electrical Repairs
Table 8.1 shows the symptoms when there's incorrect resistance in any of the resis-
tors.
Missing or H651-
broken. H654
R609 Lit
R610 Not lit
R611 Faintly
glowing
R612 Not lit
Table 8.1
• If none of the H651-H660 LEDs are lit, measure the voltage at the marked side
of R607 (~3.1V, fig. 8.4). Before measuring you have to press a key for the proc-
essor to set the LED3K signal high for about 10s.
* If the voltage is missing, make sure pin 92 of D600 (fig. 8.3) is correctly
soldered.
* If the soldering is correct, replace D600 (class B).
* If the voltage is correct, replace R607 (class A).
If the fault remains, send the phone to the next level.
8.4 The background illumination for the key-
board is missing or is faintly glowing.
Open the phone and check for liquid damages.
Make sure all the LEDs (H655-H660, 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, make sure there's VBATT voltage at the marked side
of the LEDs.
* If VBATT is missing there's a foil damage, probably due to liquid damage,
and the phone is to be discarded.
* If VBATT is correct, make sure R612 (~0 ohms, class A), R609 (~33 ohms,
class A) and R611 (~0 ohms, class A, all in Fig. 8.4) are mounted and of the
4/00021-2/FEA 209 544/11.C
H655-
H660
Not lit
Lit
Not lit
Faintly
glowing
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