JAMMA Ground Question - Newbie land

heilxmq

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Ok, still learning stuff here. With a JAMMA cabinet, should I take all the grounds to the ground of the Power Supply?

I noticed the coin slots have a ground going just to a screw attached to a big metal piece. Should I move that down to the ground on the power supply? What is the standard practice for grounding these items?

JAMMA harness - Attached to power supply ground? (Most connections are just daisy chained together. I think I read that was normal.)

Coin slots - Currently just attached a metal plate? Is this right?

marquee light - Think that has a ground attached to the power supply ground?
 
Ok, still learning stuff here. With a JAMMA cabinet, should I take all the grounds to the ground of the Power Supply?

It depends on what you are asking. The ground wires on the JAMMA connector will be used in various places. There are typically 4 on one end and at least 2 on the other end. It's always best to have at least one from each end to the DC ground of your power supply. others will go to your coin and control panel connectors for grounding of the various switches. Any unused ground wires should go to your DC ground on your power supply

I noticed the coin slots have a ground going just to a screw attached to a big metal piece. Should I move that down to the ground on the power supply? What is the standard practice for grounding these items?

This is a Free Ground (FG) connection to keep stray voltage from charging anything metal that can shock the player. This is normally connected to the free ground prong of the plug, usually through connections that eventually tie into the FG lug of the line filter.

JAMMA harness - Attached to power supply ground? (Most connections are just daisy chained together. I think I read that was normal.)

Read my first answer.

Coin slots - Currently just attached a metal plate? Is this right?

Read my 2nd answer.

marquee light - Think that has a ground attached to the power supply ground?

Read my 2nd answer.
 
Is the Free Ground on the power supply normally connected to the regular ground on the Power Supply? That's the way mine is now. For some reason that doesn't seem like it would be right to me.
 
Ok, still learning stuff here. With a JAMMA cabinet, should I take all the grounds to the ground of the Power Supply?

Normally 1/2/A/B go to the power supply DC ground, and 25/26/e/f go out to the control panel and coin door common grounds.

You don't want to attach the EARTH ground to the DC ground.
 
I'm going to work on it a little today and detangle what's currently in place and swap a few connections from the old JAMMA. I'll let you know how it goes.

I may post some pics if I get to the point where I'm going to power it back up. I don't want to fry a PCB. I should be getting a SF II here shortly.
 
Ok, did some rewiring today. Here's my understanding of how the grounding works. Please correct me if I'm wrong.

-Grounds from the JAMMA harness should be connected to the DC power supply GND.

-Do not connect the DC power supply GND to the FG.

-Do not connect the DC power supply GND to the metal case of the AC Filter

-The FG on the power supply should be connected to the metal case of AC Filter.

-The Ground line from the AC plug should connect to the metal case of the AC Filter

-The metal from the Coin doors and Control panel should connect to the metal case of the AC Filter

-The Marquee light ground wire should connect to the metal case of the AC Filter

-Transformer? I don't need one because I have a LCD monitor hooked into a RGB convertor.

Accurate? Yes/no/maybe?
 
Interestingly enough. Yesterday, after rewiring everything I was having major video problems. I left the FG on the Power Supply not connected to the GND on the power supply. I figured this was the proper way to set it up. Video wasn't working. I would get a static distorted screen. Once in awhile it would sync up and I'd get a fuzzy picture that looked right.... just fuzzy.

Today for kicks I decided to connect the FG to the GND on the power supply. Amazingly, that cleared up everything. I even tried out a new SF II PCB I got off ebay for $12 bucks and amazingly it came in crystal clear.

So now the question is..... Is my power supply bad or is this expected behavior? I haven't had much faith in this power supply or filter since I got this cabinet so I might just replace them anyway. I've replaced just about everything else. :)
 
Sounds like Video-GND (pin 14 on JAMMA) was not properly hooked up. On some bootleg boards that pin is not connected... they assume it will be grounded in the harness.
 
On the JAMMA harness I bought the video ground has a wire going to all the other Grounds on the JAMMA harness.
 
The video ground should go from the PCB to the monitor. In some cases you'll also find it jumpered to the other logic grounds in the harness.
 
Right, I think that's how mine is. It goes to the monitor hookup but is also jumpered to the logic grounds.
 
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