Asus N73 no sound in internal speakers

[Cyrielle]

Hello everyone !
First of all, I wanted to thank all the badcaps forum users for all the info and help they provide. This has helped me from going to electronics hopeless newbie to plain newbie

Problem: No internal speakers audio
Note: Audio in headphones is ok.
(Audio chip: Realtek HD Audio [ALC269])

The laptop: ASUS N73JQ
Note: I bought it out of order off ebay. I have never heard the sound work properly.

Laptop schematics: https://ufile.io/r4ajn
Not exactly the same model but very close

I thought it was a driver issue and installed W7 and W10, and lots of different drivers. No luck
I have removed and tested the speakers, they work fine.

One very important thing is that the speakers do NOT work in the BIOS either. The Asus BIOS start sound plays fine in the headphones, but no audio in internal speakers. No sound at BIOS level probably means it's not a driver issue.

The very best I managed to have at some point is:
- If I remove the battery and remove the power jack, then replug the power jack and start the laptop, the speakers will go "pop" both for the BIOS start sound and then when Windows startup sound should play. A short pop. That's all. All power must be drained again to manage to have the "pop" sound.
- On two occasions, I managed to have the first two notes of Windows startup sound play over the speakers, then "pop" and then no audio.

At this point, I think the problem may be a failing component (Capacitor?). Please help me investigate as I am not sure what I should do now.

Thanks in advance

Cyrielle

[kodox]

Re: Asus N73 no sound in internal speakers

Had you tried connect headphone directly to pin 3 & pin 12 of U3701?
If you heard a sound on headphone, U3701 probably damaged. Last test, remove R3721 & R3722 and connect directly the speaker to pin 1 of R3721 and other end of speaker to pin 1 R3722

[Cyrielle]

Re: Asus N73 no sound in internal speakers

Thank you for your help, kodox. Much appreciated. I will investigate the amplifier.

I wanted to let you know of an important further symptom. Looking for signs of life in the speakers, I realized that only the speaker that is plugged in the right speaker connector will "plop". The speaker plugged in the left speaker connector does not output any noise.

If I plug the left speaker into the right speaker connector, it will plop. So I guess the issue is even worse with the left channel.

Does it point to a specific component in particular?

[kodox]

Re: Asus N73 no sound in internal speakers

Because audio on the headphone is normal, i prefer to narrow the problem to U3701, because U3701 is the amplifier for the internal speaker, for the headset, audio signal is produced on U3601

[Mazorca]

Re: Asus N73 no sound in internal speakers

Needless to say, did you check impedance on each speaker? Both should be very close in value. Usually, when I have this same issue, if there are two jacks, mike and earphone, I remove the earphone jack and replace it with the mike jack. Unfortunately, most late laptops no longer have the mike jack.
I just saw your motherboard, looks like mike and earphone jacks are different sizes.

[Cyrielle]

Re: Asus N73 no sound in internal speakers

@kodox: your pointing to the amplifier does makes sense. I will troubleshoot it as you advised but I need time for the operation since it is a bit tricky for a newbie

@Mazorca: impedance for both internal speakers is 4.6 ohms quickly dropping to 4.3
Can you clarify how swapping mike and headphones jacks would help?

I may be wrong but I don't think the problem is with the audio jack. The Realtek software does detect and report properly when a jack is connected or disconnected.

At the moment the issue is:

• Left internal speaker: no audio, no noise, no pop, no nothing
• Right internal speaker: no audio, will go "pop" on certain circumstances

[Cyrielle]

Re: Asus N73 no sound in internal speakers

I had time to investigate around the amplifier. I tested the components around it with a multimeter in continuity mode.
See the results in the picture below
[for reference, schematics can be found in my 1st post above]

I hope it can help narrow down the problem. Apologies in advance if it's not relevant, since I am a newbie.

[piernov]

Re: Asus N73 no sound in internal speakers

On the speaker amplifier IC U3701:
If you have an oscilloscope, probe on the audio input (LINN/LINP, RINN/RINP) to make sure the audio signal is making its way through.
Then probe on the audio output (OUTNL/OUTPL, OUTNR/OUTPR).
Without an oscilloscope, a good multimeter with a bar graph will also allow to watch the variation of the audio signal on the bar graph. Some also have a dBm mode but I don't know if it'll help, depends on the amplitude of the input signal.

Will also help if you measure the voltage on all the pins.
Or if you don't want to bother, just replace the chip.

[Cyrielle]

Re: Asus N73 no sound in internal speakers

I am still testing this PC, which still has no sound on the speakers. (sound on HDMI, Bluetooth and headset is ok though).
Now I have discovered something very weird. There is no sound at all on the speakers. But if I run the PC on battery only, when the battery is at a critical level, I can hear the sound on the speakers for one second just before the PC shuts down! This is the only moment when the sound works on the speakers. What the heck!?
Can anyone explain this?