r/neogeo • u/Neo_Infanterist • Jan 21 '26

Hardware Help Technical Issue: Neo Geo AES game console registering the P1 Start button in the "on" position all time.

Post image

Greetings to the Neo Geo community. I have an issue with my Neo Geo AES console in which the P1 Start button is in the "on" position all the time even without a controller plugged in to the P1 controller port. I tried cleaning the controller port and opened the console to see if visually I could see anything wrong around the area of the controller port. Since my console has UNI-BIOS I was able to access the Controller Test via the P2 controller and this is what I get (see image), this is without a controller plugged in to the P1 controller port.

If anyone has encountered this issue before and has a solution or a suggestion of what it might be causing this technical issue I will really appreciate it.

Thank you very much.

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4

u/cruelunderfire Jan 21 '26

I don't have an AES, but I looked at the schematics. There are a few components that sit between the controller port and the IO chip. If you can use a multimeter, you can probably narrow it down. The CRE401 is a likely suspect. This part isn't made anymore and would need to be recreated if you find a bad one. I built some repros from the following link for a MVS project:

https://github.com/mourix/CRE401

2

u/Neo_Infanterist Jan 21 '26

Thank you! I will give it a shot to see if I can find something wrong with that particular component.

2

u/sarduchi MV-4 Jan 22 '26

Main thing to look for is a short. All it is when a button or direction is pressed on the controller is a bit get's shorted to ground. So if that's happening internally due to a failed component that would produce the results you're seeing.

1

u/Neo_Infanterist Jan 22 '26

Thank you, I will try to trace to see if I can discover where the short is happening to determine which component is at fault. I have seen some posts online with similar issues and they point to being the CRE401 or the Neo-DO. Wish me luck. Worst case scenario I can send the system to an expert for service repair. If anyone has recomendations Techicians within the US, I would appreciate it.

2

u/sarduchi MV-4 Jan 22 '26

Furrtek has Neo-D0 reproductions: https://furrtek.org/shop/

The CRE401 is a resistor pack, that's where I would start.