So about a month ago, I started down the path of doing a restoration of my NES, starting with a full cap replacement, then installing NES RGB. During these weeks I've had it working several times, ended up in a long battle with the power modulator box where the unit kept on burning up replacement bridge rectifiers.
After a long week or so of troubleshooting that, I threw in the towel on troubleshooting it, and decided to purchase one of the Merlin Shaw power module "companion boards". It arrived yesterday, and I soldered it into place, put my ground wire in, and it was working great (no sound issues).
I had been in discussion with Merlin on how to setup the unit so that I can still utilize the composite inputs he has included on the units (but keep RGB working), and I was changing the settings to the way I was instructed, and all that I can recall doing when the problem arose was adjusting the switch for internal/external video and audio to try to get that working with composite, when this problem decided to show it's face. Could of just been random timing though. It was within a few mins of my first test.
Since that moment, I have had a high pitched audio tone that I've been trying to narrow down what the root cause is, buuut it is working, and working well outside of the obnoxious high pitch tone that won't go away.
I've tried SOooo many things. I've pretty much redone/undone my work 2-3 times to no change, checked my soldering (had Merlin check it), rewired my multiout port which I was initially installing for use, and even uninstalling my multiout port and utilizing the Genesis 2 output port which comes on this unit. I've also removed all pallete switch wires, expansion audio, and Version 4.0 fixes for color sync issues, and I can say none of those things we're contributing factors.
The tone does not seem to alter with me touching around or poking things on the board (or hovering my hand around), wiggling wires (carefully), I've reflowed joints more times than I can count thinking cold joints might be the cause , also checked continuity. It's not really making itself apparent where it's coming from. No burnt components or signs of an issue.
When troubleshooting with Merlin, he did have me unwire the NES RGB completely of audio, and switch the unit to internal audio, and the tone is present there too, so it's safe to say maybe something to do with the audio power rail? or how it's handling the upgraded power (guessing). I've also redone my ground wire several times on the unit. I even tried fully disconnecting my palette selection wires, and expansion audio resistors I was running to eliminate those as a possibility.
Someone earlier on reddit, had asked me what the frequency was of the tone, and I tested it with a phone app, and it was 15.6-15.7 hertz, which he later stated was the frequency for horizontal sync, to which he stated "Sounds like you're getting coupling from either composite video, luma, or C-sync."
Based on this info he stated, I later tested (today) to cut a little section of my audio and video pins that lead into the power module just to rule out an A/V feedback loop of sorts. It unfortunately did not make it go away still.
Only thing I can really think is maybe something got out of whack when introducing a cleaner power source or something on the power module went wrong.
One last thing to add, I also bought a PHC AC-93a unit to use with this. One Merlin had recommended. It works very well, but it's not solving the audio tone issue i'm having. Issue occurs with known working OEM ac adapter anb brand new PHC AC-93a model adapter.
It's basically working 100% now, minus a 15.6 hertz nonstop audio tone you hear during any quiet parts of a game or in menu selection.
Anyone have any suggestions or things they can think of I might check?...
