Strange issue with controllers

[philjay]

Hi guys,
i have a neo geo 3-5 with a strange issue. I have on both controller port the D button always pressed. Obviously i checked other pad and joystick but i have the same issue.
The problem is present just when the controller is inserted, and when a cart is inserted. I checked the voltage without any cart and with button pressed the voltage is changing from 5v to 0.
I have already changed the ferrite on the d signal, the related cr401 - that was working according to ohm - and the c1. Always the same problem.
Anyone have any idea?

Thank you

 

[Neo Alec]

Is the problem present when no controller is plugged in? Did you test with more than one controller?

 

[philjay]

Yes, tested 3 controllers and is the same, tested in other neo geo the problem is not present. The issue is present just when the controller is inserted, one or both is the same short on D

 

[city41]

What happens with no controllers attached, and you short inputs (especially D) with a wire? Do they act normally?

Just make sure not to short the 5v pin.

 

[city41]

This post might also be relevant here

Neo Geo AES stuck on button test screen :(

Hi guys, I recently picked up a Neo Geo AES to replace my broken one, however this one seems to broken as well, when I put in a game and switch it on, I come up with this screen. I tried it with different PSU and only the one that came with it works. All the games seem to boot into this...

www.neo-geo.com

Yes, that screen comes up because ABCD on player 2 are on. The point is what is causing the short? The controller inputs are handled by the PRO-B0 which is that big square custom IC in the middle of the PCB. The only things between that and the joystick ports are the resistor networks and a short in one of those is very unlikely, let alone in four of them (there are 9 inputs on). This points to a problem with the PRO-B0 itself. If you add that the green screen he's getting without cart points to a color ram error and that the color ram is also handled by the PRO-B0, the IC is likely to be faulty.

 

[BIG BEAR]

It reads like a GROUND line and your D button line are coming in contact with each other somewhere.
Grab a multi-meter and touch your ground pin and D pin at the port to see if you get continuity.
If you get continuity ,find the point where they come in contact wlth each other and break their connection.
BB

 

[philjay]

No, the problem started just when a cart is inserted and obviously with console powered. Checked the c1 and the point on controller and when a cart is inserted is shorted, without working normally 5v to 0 when pressed.

 

[BIG BEAR]

No, the problem started just when a cart is inserted and obviously with console powered. Checked the c1 and the point on controller and when a cart is inserted is shorted, without working normally 5v to 0 when pressed.

Did you replace the C1?
BB

 

[philjay]

Yes, c1, ferrite and cre401. Same issue. Could it be the d0?

 

[BIG BEAR]

Yes, c1, ferrite and cre401. Same issue. Could it be the d0?

No.The d0 is audio related.I still think it's a ground issue somewhere.
BB

 

[BIG BEAR]

Yes, c1, ferrite and cre401. Same issue. Could it be the d0?

Did you or are you able to go into controller test mode?
Controller in port 2 and press all 4 buttons before you turn on the unit?
BB

 

[philjay]

Yes, and i see the d stuck on both controller, it’s a tricky problem, other buttons and directions have no problems

 

[philjay]

The tricky part is the same button on 2 ports

 

[city41]

The wiki does say that the d0 is used for controller input

NEO-D0 - NeoGeo Development Wiki

wiki.neogeodev.org

 

[BIG BEAR]

My bad on that. I've never had an issue that involved changing out the d0.Try changing out the d0 then .
BB

 

[philjay]

I saw that, will try tomorrow and keep you informed. Thank you

The wiki does say that the d0 is used for controller input

NEO-D0 - NeoGeo Development Wiki

wiki.neogeodev.org

 

[philjay]

Hi guys, fixed. I just reflowed the D0 and issue gone.

 

[philjay]

No, actually the problem is very strange. With original bios works perfect with unibios not. Tested 2 unibios and i have the same issue.