does everyone have frame ground issues ?

r5g

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is it just me or does everyone have frame ground issues when building new games?
ok when i make up new cabinets, or used cabinets and sometimes use old school rgb low res monitors, or sometimes lcd's, and different makes and models of power supplys i almost always have issues with frame ground and have to experiment to see what the game likes lol. why is that? you would think it should be universal, a frame ground is a frame ground and should not matter what brand of monitor power supply ect?
but it does!
today making up a multi game i used frame ground on the lcd and power supply, and on cabinet wiring only to have it fry the ground wire coming from the jamma pcb to power!
remove the frame ground from the lcd, and then its ok !
other times i have had frame ground connected and it causes game and or power to reset?
removed it and its ok!
other times i have needed it connected to get rid of trace dots floating in happ monitors ?
and then again sometimes it needs to be disconnected to get rid of those?
any tech gurus have all the answers for frame ground?
 
I've only had about 6 games but none of them had any problems with grounding the frame of the monitor. Are you using the earth ground terminal on the power supply? Or are you using just one of the common grounds off the jamma harness? It's supposed to be grounded by the earth ground.
 
Earth ground (the third prong on the AC cord and the case of the power supply, and probably what you should be grounding the monitor frame to) is NOT the same as logic ground (found on the black wires of the JAMMA harness. If you tie the two grounds together (or try to use the wrong one), you'll create problems.
 
The monitor's frame, the isolation transformer's mounting frame, the power supply's FG terminal, and really all the metal stuff in the cabinet (coin door, CP, etc) - they should all be connected to the third prong (earth ground) on the AC cord. Never ever ever connect logic ground (like the CP button ground, or the black ground wires in the JAMMA harness) to frame ground.

Edit: You might try using your meter to check to see if your earth ground is really ground. Set it on AC volts and put one lead in the round third prong hole, and one in the wider blade (neutral). You should get zero volts, or very close to it. If you don't, then your earth ground has some voltage on it, which would indicate a wiring problem. If you get 120v, that would indicate that the hot and neutral are swapped. But some other voltage, like 20v, could indicate some other problem. In many cases, it's a disconnected ground somewhere else, and that prong really isn't grounded, but there's some other device on the same circuit that has ground leakage, and it's raising the potential on the third prong.

-Ian
 
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I've never had any wires burn up, but I've definately had interference.....and no rhyme or reason.....just as you noted. And I know the difference between logic ground and earth ground. I know those two grounds shouldn't be connected. Here's my additional questions to this......On pinball machines, the earth ground and the logic ground are connected......also...on monitors (paticularly older models)......earth ground and logic ground are also connected....via the dag. The dag (usually) plugs directly into the neck board.....thus joining logic ground........but it also wraps around the metal frame and the mounting ears.....thus joining it to the metal, and ultimately, earth ground (if you connected earth ground to the metal frame).

Edward
 
ground

sounds like parts engineers sometimes connect earth ground and logic ground internally, and sometimes not, maybe this is the problem?
if i check with a meter to see if they are connected on items like the power supply and monitor would this be a solution to not use the frame ground when i detect they are connected, and use it if they are isolated?
 
sounds like parts engineers sometimes connect earth ground and logic ground internally, and sometimes not, maybe this is the problem?
if i check with a meter to see if they are connected on items like the power supply and monitor would this be a solution to not use the frame ground when i detect they are connected, and use it if they are isolated?

I've noticed this too. PC motherboards in particular seem to always have the mounting holes shorted to the PS ground, shorting logic ground and earth. Why?
 
sounds like parts engineers sometimes connect earth ground and logic ground internally, and sometimes not, maybe this is the problem?
if i check with a meter to see if they are connected on items like the power supply and monitor would this be a solution to not use the frame ground when i detect they are connected, and use it if they are isolated?

I have had similar monitor grounding issues on some cabs and found connecting GND and FG together, cleared it up.

Thats only some 'odd ball' cabs... confuses me, so i can confirm your feelings on this.
 
I have a power supply here that says the following on it:

WARNING: Do NOT connect power supply frame to Field Ground. Only connect it to the FG connector.

Maybe you have a similar power supply issue?

Frame ground should never be connected to logic ground. Bad things can happen when you plug the game into a miswired outlet.
 
grnd

in my case the bad things are happening when i plug in fg of lcd monitors, (green wire from power cord) to fg terminal on power supply (or should the green wire on power cord in monitor be connected to gnd terminal?)
the fg on the terrminal is also connected to most of the metal in game, and the green ground wire from ac line
when i do this, the logic ground has massive current, (smokes) and the games voltage drops.
i have checked my outlet, its wired correct, i have checked the games line cord, its correct too. what is going on here?
 
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in my case the bad things are happening when i plug in fg of lcd monitors, (green wire from power cord) to fg terminal on power supply (or should the green wire on power cord in monitor be connected to gnd terminal?)
the fg on the terrminal is also connected to most of the metal in game, and the green ground wire from ac line
when i do this, the logic ground has massive current, (smokes) and the games voltage drops.
i have checked my outlet, its wired correct, i have checked the games line cord, its correct too. what is going on here?

I think that's your problem. You're powering your LCD monitor off the power supply. I think it needs it's own power source. It should be plugged in directly into a ac outlet.

Your lcd monitor doesn't need to be grounded from the FG terminal of your power supply since it is already grounded from it's power source
 
power

its all in parallel so its all the same isnt it?
i mean yes the line cord goes to the ac inputs of brick type switcher power supply, and green from line cord goes to fg on power supply, and yes i was just connecting the line cord of the lcd to these same ac inputs of the power supply, and green from lcd to fg, but even if i was not, electrically its the same as it would just be in parallel anyway? compared to if i had the lcd plugged in separate, (connecting to same electrical point just at a different location)
 
its all in parallel so its all the same isnt it?
i mean yes the line cord goes to the ac inputs of brick type switcher power supply, and green from line cord goes to fg on power supply, and yes i was just connecting the line cord of the lcd to these same ac inputs of the power supply, and green from lcd to fg, but even if i was not, electrically its the same as it would just be in parallel anyway? compared to if i had the lcd plugged in separate, (connecting to same electrical point just at a different location)

Try it. For some reason I think it matters.
 
I have a power supply here that says the following on it:



Maybe you have a similar power supply issue?

Frame ground should never be connected to logic ground. Bad things can happen when you plug the game into a miswired outlet.

I've seen that warning on a lot of switchers.......but here's the rub......If you connect the monitor's metal frame to earth ground (as most, if not all, are done from the factory)......you are now connecting earth ground to logic ground, thus, those two points on the power supply are now connected.

Edward
 
power

interesting follow up
it seems the vga connector cable is the culprit
it shorts fg to logic ground internally via the pinouts, and the fg is isolated in rest of cab
with it (vga connector) connected, the fg wire of power cord to lcd has 0 ohms between logic gnd and fg
with it taken off the ohms are about 150
with fg wire of power cord connected to gnd, or disconnected all works well
with fg of power cord connected to fg of rest of cab , there is constant resetting, and drain of current thru power supply.
there is 10vac, 5vdc potential between fg and gnd in this cab with it isolated, have no idea why, but these are shorted together when fg of monitor power cord is connected to fg of power supply and cab,
so for now with happ power supplys and lcds i am going to run the fg of power cord to gnd on power supp
 
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Frame ground should never be connected to logic ground. Bad things can happen when you plug the game into a miswired outlet.

So, what, every PC motherboard manufacturer under the sun is doing it wrong? Or do the many multimeters I've used over the years betray me, and the screw vias aren't actually connected to the black wires on the ATX connector? Or is this a switcher thing?

And really, what damage would crossing line and ground do? Unless you have a defective breaker, that's about all that's going to happen -- house breaker pop.
 
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I've never had any wires burn up, but I've definately had interference.....and no rhyme or reason.....just as you noted. And I know the difference between logic ground and earth ground. I know those two grounds shouldn't be connected. Here's my additional questions to this......On pinball machines, the earth ground and the logic ground are connected......also...on monitors (paticularly older models)......earth ground and logic ground are also connected....via the dag. The dag (usually) plugs directly into the neck board.....thus joining logic ground........but it also wraps around the metal frame and the mounting ears.....thus joining it to the metal, and ultimately, earth ground (if you connected earth ground to the metal frame).

Edward

I was just dealing with this for at least the 2nd time. I added a switching power supply to pac cab tying the FG to Earth GND coming into cab, and the GND to the my pac adapter board. Immediately had super bad interference on the monitor. Disconnect gnd from monitor frame and it gets better but not 100%; disconnect FG from PS and it is 100%.

What I found is that the plain GND (assumed logic gnd on power supply) is getting tied to the monitor frame already via the harness somewhere in the cab (maybe by the gnd on video cable which as ed mentions is tied to frame) and when gnd cable is hooked back up to the monitor frame the PS logic GND is now tied to Earth GND. If you also hook up the PS FG to Earth GND (as it should) Logic and FG are now connected and the Switcher really doesn't like that.

I have read like 10 threads debating all this and it still doesn't make sense to me. All I know is stuff is gnd'd and disconnecting FG from power supply solved my monitor snow and sync issue, which didn't exist before putting in switcher.
 
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WMS attached FG to logic ground on many of their late 80's and 90's games. I recall seeing a jumper on the switcher on MK's when they were brand new.
 
WMS attached FG to logic ground on many of their late 80's and 90's games. I recall seeing a jumper on the switcher on MK's when they were brand new.

Jumping switchers FG to GND? That makes some sense as I have seen it before on my karate champe but thought it was wrong, so removed it and got interference on the monitor. Tying them together probably eliminates any of the variance of some leaking voltage or resistance seen the separate gnds.

Will defer to others but I am not sure if disconnecting FG is better or worse than tying them together.
 
FWIW, whenever I see noise on the monitor and the game has a switcher I tie FG to logic GND. I've never had a problem doing it, ever. I've been a CoinOp tech since 1984 and have done this 100's if not 1000's of times.

Also.... Different subject but same smell.

connecting into the monitors supply to supply other 120VAC items in the cab (power supply, light fixture). Everyone says its a no no.... Look in the back of a Baby Pac Man... Bally did it.
 
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