Low buzzing sound on modded famicom

[fredJ]

I have a constant low buzzing sound on my famicom. It isn't the second port controller, I have tried removing it. I wonder what it can be? Maybe it is even supposed to be this way, or no?

If not, I wonder if it may have something to do with the grounding. I have attached both the audio and video grounding to the GRN on the PCB. The sound wire comes directly from the SOU output and that's it for sound: two wires.

Could the wiring for the video cause the sound buzzing somehow?

[ericj]

You may want to try grounding it to a different spot, but it's possible that a bad RCA cable is causing the issue, too.

[Xious]

Seconded: It appears to be either a bad ground, or a mixed signal. You should also check the actual source of your audio signal, and ensure your solder-points are all clean. 

[133MHz]

Try another AC adapter if possible.

[fredJ]

Thanks for the suggestions, I will try different things..

Is there any low buzzing noise on any of your famicoms? If you are at the intro scene or somewhere with no music, and turn the volume up? I have heard that if may be unavoidable with noise intereference on the famicom because of how it is wired.

On my Twin Famicom there is no buzzing at all anyways.

[Xious]

I have had this happen on one system out of hundreds that I've restored, where nothing would remove the buzzing, even restoring the controller. There was a problem in the audio circuitry, but I don't recall what i did to remedy it. Usually, it's just the microphone and restoring that will remove the static.

Check your ground and signal solder points first... Where are you connecting the RCA wire ground and where are you tapping the audio signal? You should use the GND test-pad, and the mixed-audio signal from the bridge-connector for the optimal results. If you need help locating these, let me know. It would be helpful if you tell us what revision Famicom you are modifying. The Rev number is etched into the PCB and is also on the silkscreen layer for non-VCCI models. If you need help locating the revision number, please ask.

I think I'll make a topic for how to do this, and several other sticky-worthy topics a 'how to identify your exact Famicom model and revision' thread would probably be useful for this board. 

[fredJ]

With mixed-audio signal you mean SOU, right?

(I have the -07 model)

[Xious]

With mixed-audio signal you mean SOU, right?

(I have the -07 model)

No, you don't want that pad: That's pre-mixed audio.

You want the audio pin on the bridge connector. Download the manual here:
RetroVideo Documentation

Once you have the PDF, look for the section on wiring Mixed Sound, and follow the instructions there. The correct pin is illustrated in detail.

[fredJ]

I see. Thanks!

After the previous comment I already moved it, but wasn't sure which of the pins on the bridge-connector was sound, so I connected it to pin 46 on the cartridge slot instead (as per jpx72 I think). That should work equally well? Akumajou Densetsu sounded alright to me.

Mi5terDNA: thanks. I think you are right, there is an unavoidable ground hum. I think I have it at an acceptable level now. Either because I resoldered wires etc or possible it was the old caps that woke back to life.

[fredJ]

How do you make music with it..? 

[Xious]

There are a number of methods for making NSF music: Search for the term 'NSF' on NESDev...

It'd be nice to have an NSF programme for the FDS to take advantage of the extra FM-quality  sound on the hardware, but alas, to my knowledge no such software has been made to date...

[Xious]

That doesn't work with the FDS though, so you can't use the FM chip capabilities. Nevertheless, it's still a brilliant piece of software...

[2A03]

That doesn't work with the FDS though, so you can't use the FM chip capabilities. Nevertheless, it's still a brilliant piece of software...

Not to nitpick but the FDS sound channel is wavetable, not FM.