Ericsson PF 768 Troubleshooting Instructions page 47

PF768, Standard Electrical Repairs
correct resistance. Table 8.1 shows the symptoms when there's incorrect
resistance in any of the resistors.
• 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.
8.5 Green top indicator doesn't work.
Open the phone and check for liquid damages.
Make sure the double LED (H650, class A, fig. 8.2) is correctly soldered.
Give the board power and start it up by pressing the On/Off key.
Measure the voltage at pad 4 of H600 (~3.4V, fig. 8.2).
• If the voltage is missing, measure the VRPAD voltage (~3.8V) at pin 1 of V706
(class A, fig. 8.2).
* If there's no voltage at pin 1 of V706, check if there's VRPAD voltage at
pin 5 of N452 (fig. 8.3).
* If the VRPAD voltage at pin 5 of N452 is incorrect, proceed to chapter 3
("Doesn´t start"-fault).
* If the voltage at N452 pin 5 is correct, measure the resistance from pin 5
of N452 to pin 1 of V706 (~0 ohms).
* If the resistance is too high it's probably L450 (~0 ohms, class A, fig.
8.3) that's broken.
* If L450 isn't faulty or incorrectly soldered there's a foil damage
and the phone is to be discarded.
* If the voltage at V706 pin 1 is correct, measure the resistance from VBATT
to V706 pin 3 (~4.7 ohms, fig. 8.3 and 8.2).
* If the resistance is too high it's probably R652 (~4.7 ohms, class A, fig.
8.2) that's faulty.
* If R652 isn't faulty or incorrectly soldered there's a foil damage and
the phone is to be discarded.
* If the resistance from VBATT to pin 3 of V706 is correct, replace V706
(class A).
• If the voltage at H600 pad 4 is correct, check the soldering at pin 94 of D600.
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