SNES sound distortion issue

[marcorosa13]

Hi! This is my first post, I need some help, I have a strange issue whit my SNES model SNES-GPU-02, Look the video with glicht or distortion in sound during the games, the video it's good, but the sound doesn't

https://youtu.be/VYv96SLGXNc

I made a bridge from chip L324M to de "positive" side of one capacitor, the distortion it's gone, but i missed one channel of sound, and some sound effect during the game doesn't listen!

Any HELP PLEASE!?

[lidnariq]

Get the schematic at https://wiki.superfamicom.org/schematic ... nd-pinouts

Using an audio amplifier, trace the audio path from the output to the DAC, or vice versa, and see where the distortion appears.

[marcorosa13]

Sorry, I'm a rookie with all this! It's to hard reading the schematic ! I tought It was more easy to fixing

I Change the LM324 chip, and the AUDIO 2-CHANNEL 16-BIT D/A CONVERTER, and the issue still there!

[Fisher]

Which pin of the IC you had put on what pin of wich capacitor?

The problem may be a bad electrolytic capacitor.
Since they're 20+ years exchanging them is a good idea.

There's also a small circuit with a transistor and some other components, that you can test with a small amplifier as Lidnariq suggested.

[marcorosa13]

[img]https://drive.google.com/file/d/1R4mkQz ... ivesdk/img]


From pin 1 to the positive side of capacitor! The distortion its gonr but there are some missing sound, or sound glitches,


PF: After doing this, I replace all the capacitors and nothing happend,

[Fisher]

Unfortunately, I'm not able to see the image that you have posted.
Looks like you are plugging the output of the left post amplifier to the positive of an output capacitor.
There is a big chance of some problem on the transistors Q16 and Q17 or on the circuit around them.

Have you tried another known good power supply, or even this one on a console that is working fine?
A bad one can cause many weird problems.
As you can see on the schematics, the VRef of this amplifier comes from a small transistor straight from the power supply.

It's also a great idea to do the tests that Lidnariq suggested and see if you can discover where the noise begins to happen, that will sure be a nice starting point.

[Nikku4211]

Unfortunately, I'm not able to see the image that you have posted.

I just clicked on it and I can see the image.

[marcorosa13]

I changed the properties now you can see the image.

I changed those capacitors, around the IC and nothing

My power supply its the same I used to in other SNES without problems

[Fisher]

Now I can see it, thanks.

Basically you had put the left channel post amplifier output on the right channel output capacitor.
I'm not sure if in this kind circuit is a good idea to do these trial and error stuff but, does it make any difference if you plug it on the C66 instead of the C65?

Again, I'm asking you to try the tests that Lidnariq said to try to narrow the problem.

[marcorosa13]

I been tried with other capacitor, and nothing!
And I sorry I can't understand the schematic that the other user mencioned

I won't able to think that the IC of sound or cpu its damage!

[Fisher]

As I've seem on your YT channel, your mother language is probably spanish, right?
The schematic is very well designed and simple to follow.
You can post your doubts here and I'm sure people here will be happy to help.

But try first to follow the signal with an amplifier, as suggested by Lidnariq.
This will give good clues about what is happening.

Looks like it's not related to the sound APU, probably just some problem with the post amplifier circuit. Since you've got no audio after bypassing part of the output circuit, that's probably where the problem lies, but it needs further testing to have a better idea of what's wrong.

[marcorosa13]

Thanks Fisher! Thanks a lot! Yes I'm from Argentina!

And I will try everything you said, to fix the console!

Can you check to my another post, about the another SNES I have with problems!