Neo Geo 3-4 Strange Audio.

[letsgomexd]

EDIT: FIXED

I have a Neo Geo AES 3-4 Board. I am getting very inconsistent audio. For example in some games it is fine for 5 seconds then it glitches out. Then in Metal Slug 3 and others I get nothing at all. Some games just the music is missing. Some games the first audio clip that plays loops forever. Here is a video of what my console is doing:

Things I have done to try and fix it:

• I have socket-ed and replaced the Z80, the BIOS (replaced with unibios), the Yamaha YM2610, and the Yamaha YM3016.
• I cleaned the cartridge connector the deoxit.
• I checked every leg of the z80, and YM2610 with a multi meter to see if it was connected to the cartridge slot and that is supposed to be connected between the two chips. (Seemed correct)
• 3-3 3-4 Audio Fix for Headphones
• Recapped the full console.
• Switched to High Quality Triad Power Supply
• RGB Bypass (Not really to try and fix the audio, but I have done it)
• edit: Tried to use an official cartridge.

Everything seemed to check out. I get no difference with any configuration of new chips and old chips.

Limitations I have in diagnosing at the moment:

• I only have an rgb scart cable that take audio out of the headphones. (I don't know if this is an issue that could only be on the headphone output)
• I only have a NeoSD Pro and no official carts. (I have tried a bunch of different sd cards and flashed games to different slots. I also tried using the ram slots.)
• I don't have another console to test the cart with. (I can't imagine it isn't the console though)
• No diagnostics bios / cartridge.

Pictures of my mod work and board:

https://imgur.com/a/hmBSzZM

Please let me know if anyone can think of anything it could be. Or even what the next step in my testing should be. I have put a lot of time into this console and I want to make sure I am taking the right steps going forward. Or that I didn't make a mistake / miss anything obvious.

Thank you in advance to anyone who takes the time to read this. I have really fallen in love with this console and I want to see it working again one day.

Edit: Thank you mods for moving this to the correct category

 

[Neo Alec]

It could be the NeoSD. Need a real cart to rule it out.

 

[letsgomexd]

It could be the NeoSD. Need a real cart to rule it out.

Okay, I ordered a cheap World Heros 2 cart off eBay. Should be here in 3 days. I'll post another video when I can. Thank you. Thank you everyone who dmed me as well.

 

[letsgomexd]

Took forever to arrive even though I paid extra for priority mail

There is no sound at all other than the noise you would expect with analog audio. As I thought it was the console. What should I look at now going forward? I have a scope if need be.

Here is a video:

 

[Neo Alec]

I assume you cleaned the cart with Deoxit. That stuff is my go-to to make sure it's clean.

 

[letsgomexd]

I assume you cleaned the cart with Deoxit. That stuff is my go-to to make sure it's clean.

Yes I did. I love deoxit as well it has fixed so many issues for me, but I think it is pretty safe to say at this point it isn't a cleanliness issue.

I looked at the PCB for the World Heros 2 cart I have and it seems to have the NEO-ZMC2 chip required to make a diagnostics cart. I ordered the materials for that from RetroGamerStuff. I am going to wait for that stuff to arrive. If anyone has any other ideas of things to try while I am waiting for it please let me know.

 

[letsgomexd]

I didn't know the 240p Test Suite for the Neo Geo is so detailed.
I did a quick run through of that and recorded a video. My Yamaha checks all seemed good but the Z80 Ram Test came back as timed out.

I have 2 questions after going through this though:
Is the SSG channel 3 supposed to be noise? I read on the wiki it has 3 square wave oscillators and then 1 noise, but the test suite only has 2 squares and a noise for me at least.
Is it worth it to replace the z80 ram just based of this? The chip is cheap so it isn't a big deal or should I just wait for the test cart materials? I don't know how accurate this test is.

ALSO: SHVC-1A1M-01 SNES cartridges have the same BR6216A-15L SRAM chip. I imagine if you had one on hand and you needed this chip you could replace it since some of the games are worth less than a dollar. https://snescentral.com/pcbboards.php?chip=SHVC-1A1M-01

 

[letsgomexd]

Update: I fixed it.
There was a broken trace connecting the cartridge slot to the SRAM chip. I found it when I was installing a socket. If you have an issue similar to mine check pin 14 of the SRAM chip. I wish I didn't buy all the materials to fix it that I did, but you live and learn.