Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
62(78)
The reference voltages at N500 should also be measured, they should be:
DEC 2 /1.2 V
DC
(C511), DEC 3 /1.7 V
DC
(C510) and REXT 1.2 V
DC
(R507),
if not try to resold the components or replace them depending where the fault is.
If all of the actions above have been done and the conclusion is made that some of the circuits
N501, N500, D600 or D500 is faulty, a self-test of the phone in EFRA could be useful to
determine which of the circuits that could be faulty.
17.7 The CPU loops are out of order
When the CPU loops are out of order it is only the audio paths “ATMS – CPU – AFMS” and
“Mic – CPU – Earphone” that are faulty.
The other three should work.
Open the phone and check for liquid damage.
The fault is usually due to D600, but sometimes D500 or N500.
Also check the signal paths: DSPULD and DSPDLD.
If all of the actions above have been done and the conclusion is made that some of the circuits
N500, D600 or D500 is faulty, a self-test of the phone in EFRA could be useful to determine
which of the circuits that could be faulty.
17.8 Both the CPU loops and the PCM loops are out of order
When the CPU loops and the PCM loops are out of order is it only the side tone paths
(“ATMS – Earphone” and “Mic – AFMS”) that are working.
Open the phone and check for liquid damage.
Power up the board and start it in EFRA with the test program.
Check the feed voltage VCORE.DSP.
If the feed voltage is correct, make sure R519 (PCMDLD) is mounted.
If the resistor is mounted and got correct resistance (1kohm) the fault usually is due to N500,
but sometimes is it due to D600 or D500.
A self-test of the phone in EFRA could be useful to determine which of the circuits that could
be faulty.
If the feed voltage is too low, measure the resistances of VCORE.DSP (N720) to ground
(>20 kohms).
If the resistance is correct, replace the regulator N720.
If the resistance is too low, use the circuit diagram. Remove one component at the time that is
fed from the short circuited voltage and measure the resistance after removing it.
You have found the faulty component when the resistance is raising after removing.
Do not forget to mount all the components that have been removed.
The short circuit is can be due to D500.
If the feed voltage is too high, replace N720.