Jamma+ Cabinet Voltage Problem Effecting Screen?

[cammo35]

Hi all. My first post.

I'm pretty new to collecting arcade cabinets and i have just started. So far I have a custom built mame cabinet, twin Daytona USA, Street Fighter II pinball machine and a Street Fighter II cabinet.

I am currently restoring the Street Fighter II cabinet and I have run into a bit of a problem when I swap another Jamma board into it.  Now the machine works perfectly with the Street Fighter II Jamma board, but I recently bought a Happy Fish V2 302 in 1 jamma board (I know there not the greatest). Everything seems to work fine apart from the color on the screen. Its quite dark but as soon as i move a joystick or press a button and hold it in that position the picture becomes perfect. Release the joystick or button and it goes back to being a bit dark.

I'm thinking it must be something to do with the voltage?  Any idea on this would be much appreciated.

If you need pictures of the problem or more info just let me know.

Cheers

[RayB]

Just guessing here, but check to make sure your button and joystick ground wires are NOT linked into the ground of the monitor, and also I think not to the video signal ground either.

[cammo35]

Thanks for the response, will check it out and get back to you.

Cheers.

[cammo35]

OK, so traced out the ground wires and they are not linked to the monitor or video ground. They all seem to be separate.   

Now i'm pretty new to all this. i'm an electrician by trade but deal mainly with low voltage installations not extra low voltage.  So the wiring for the controller seems to go back to a small PCB board which it plugs into. The ground wire for the controls are connected to the ground wire of the 1 and 2 player buttons and coin mech.  All which seem to run down to power supply.  But i did notice 2 wires from the controller PCB board that were not connected, a white one and a black one.  Should the ground wire for the controller be connected to that instead of the other ground wire from the 1 player and 2 player buttons?

I have tested the voltage across the ground wire from the control and there is 12v ac across it. The control wires to all buttons as well as joysticks also have 12v ac across them too.  So I'm stumped. Have been thinking all i can do is find a wire that's not a control wire and has 12v across it, tap into it and connect it to the ground wire to see if that cancels out the interference with the picture. Just don't want to blow anything up though.

Any other thoughts?

[RayB]

That's odd. My understanding is that all controls run on 5 volts (JAMMA spec).

[cammo35]

Voltage wouldn't be different because I'm in Australia and its an Australian Cab?

[grantspain]

happy fish take video ground from pins 28 not from pin 14
also has grounds on pin 28 and not pin 27,pin 27 is used as 6 button

so basically remove the ground wires on pin 27 if there are any and solder to pin 28 and then remove the video ground from pin 14 and add to pin 28

should sort it out

btw don't read voltages on ground/switches on Ac they are DC-at around 5 volts for switch line signal

[cammo35]

Hi, grantspain.  Thanks for the reply, works perfectly now. It's great having such a good online community who share the same passion.

Thanks too RayB appreciate the help.

Now must go and play some games.........