Dell Alienware M17R3 - LA-C912P - zwarcie i brak dzwięku

Laptop Dell Alienware.
Płyta: LA-C912P REV 1.0



W laptopie brak jest dźwięku z przednich głośników.
Subwoofer działa. Na wyjściu, przebieg oscyloskopowym z delikatnym szumem z cyklicznymi pikami na niedziałających glośnikach...

Zlokalizowałem zwarcie na płycie (kondensator) w okolicach wzmacniacza TPA3131 ale nie mam pojęcia co to za linia i gdzie szukać,.







Na zdjęciu zaznaczam zwarcia ( prawdopodobnie na tej samej linii).
R=~0Ohm względem Masy.

Proszę o pomoc, bo już nie mam pomysłu

dernis ha scritto:Zlokalizowałem zwarcie na płycie (kondensator) w okolicach wzmacniacza TPA3131 ale nie mam pojęcia co to za linia i gdzie szukać,.

Hello!
The short circuit on all three highlighted capacitors is completely normal. This capacitors are only EMI filter capacitors between analog and digital ground on the board and there should be a short circuit on them.
Solder all removed chips and capacitors back to its place.

There is some dirt on the board (picture below). Is this spill residues, or something else?

the laptop has a "service tag" sticker. This element was probably "moved". The edges have changed color from heating. TPA3131 was replaced. The transition from TPA to the speaker connector through the coils is.

Headphone output works. It switches correctly

Could the Creative IC be damaged ??

Clean the burned area with IPA as much as possible.

Check, if the sound is present on headphones.

dernis ha scritto:Headphone output works. It switches correctly

ok,

Sorry, I missed this.

Measure the voltages to ground on pins 1, 2, 7, 12, 13, 30 of chip UA4.

1 - 0V
2 - 0V
7 - 3,3V
12 - 0,47V
13 - 19V
30 - 0, 25V

Hm...
30pin - there are jumps to 1.5V...

Measure the resistance on highlighted capacitor (picture below).

Resistance to GND = 1,1kOhm

I don't know if it matters or it will be helpful, but how will I reverse the probes

COM to PLUS
Plus to GND

Resistance = 0,7kOhm

Measure the voltages to ground on both pins of highlighted resistor (picture below) when the machine is turned on.
If you have around 19V on one pin, and 0V on another pin, replace this resistor. The value of this resistor is 10Ω/5%, package 0603.

ok, this resistor was broken. its 2Mohm resistance ... I replaced it with a new one ... no 19V on the other side.

It's still V = 0.5V from the capacitor side

hm .. after starting the laptop ... resistance rises to 13 kOhm

The resistor is demage again

Audio amplifier chip UA4 is most likely damaged.
Remove the chip UA4 from the board and check, if resistor survives and you get 19V on the capacitor near it. If so, the chip UA4 is damaged and needs to be replaced.
Also check if the speakers have a correct internal resistance (usually around 4Ω).

the capacitor was burnt .. its resistance was 3 kOhm for safety, I changed the amplifier. After replacing the components on the power line of the LDO block, everything works.

Thank you very much for help:)

One more question. Where to buy a BL connector? Has a broken lock. I can't find one like this anywhere ...