Buttons input problem

[Gradius]

I've noticed a problem with one of my controls panels. It's a psx pad hack, using a usb adapter under win98. Sometimes, one of the buttons register input, even when it's not being pressed, and even if I remove the microswitch. I think this happens with 2 of the 6 buttons. It happens now and then, and I notice this specially when I remap the special button in shoot'em ups to one of these buttons. I'm playing normally and ocasionally the bomb or the special attack is executed. I couldn't be sure 100% but I think this happens only with MAME. I've been testing it for a while in the control panel window and these buttons don't seem to input if you don't press them. Could it be a problem with MAME? What test could I carry out so as to isolate the problem and find out the cause of it?

[reebboy]

Have you checked your default MAME key settings and make sure that the key you have assigned to the problem button is not also assigned to something else. I had a similar problem and found this to be the cause.

I had the letter "T" assigned to something like the second player RH joystick button. I couldn't figure why everytime I went to the right the game would do starange things. I found that by default MAME assigns the "T" button to the "TILT" function. So everytime I moved the joystick right I went right and tilted the game at the same time.  

[Bgnome]

it could also be due to the fact that you are using a psx pad hack.  when i built the lpt port interface, i had to tweak the scan/clock settings in the drivers to get it to work correctly.  if it was just a little off, i would sometimes get a particular button registering a keypress..

[Gradius]

But I'm not using lpt, but USB adapter under win98...

[Bgnome]

im just saying that it could be a scan/clock issue, regardless of the interface.  different settings are optimal for different controllers.  have you tried using different controllers on your adapter?