Monitor interference and AC line filters

Xyla

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I have several games that have the annoying diagonal interference lines scrolling across the picture. Some are subtle, others are intolerable. Usually people say "cap kit" and "filter cap"... but I assure you replacing caps never does a damn thing for any game of mine with this problem.

There aren't a lot of posts on this subject that I can find, but it seems some people have eliminated this interference by disconnecting the earth ground from the monitor frame. I haven't tried this yet, but I don't really want to. Obviously these games came from the factory with the monitor frame grounded, so that means something has stopped working properly since then.

Do AC line filters go bad? Could this be the cause? I'd like to know before I order a bunch of new line filters... they aren't super cheap.
 
I have a similar problem with a multi gun cabinet that I am working on.

In my case, the lines got worse as I added games to the cabinet. And they didn't exist on all games.

I am fairly certain that my power distribution system was terribly designed (by me...), so I have now ordered up a whole new host of materials to completely rebuild that portion of the cabinet.

If yours is like mine, then I think it's a ground loop. Basically your current has more than one path to ground, and due to the difference in resistance in each, can end up inducing unwanted current and noise in the wrong places. Would make sense that some solved it by removing the ground on the monitor frame, which is basically the same as removing a potential ground loop.

I ended up buying a book on the subject and after reading the book realized I'm dumber than a lot of folks out there (book was basically written for engineers lol, wasn't easy to follow). But I did take away a pretty big design tip. Any time you can, you want to use what they refer to as a "star" configuration for your grounding (actually it recommends to mirror your voltage distribution to however your ground is set up, so I suppose in a sense to your voltages too). So find a place that you can basically run all your grounds to a single point, which should then be as short a distance as physically possible to the earth ground connection of the machine. To say it a different way, hold your hand out in front of you and spread out your fingers. Your fingers and thumb are each a ground wire in the system, all coming together and connecting at your palm, and then your wrist/arm is the cabinet earth ground connection that goes out to the wall.

I ended up ordering a bunch of these to create this:

https://www.waytekwire.com/item/47217/Junction-Block-Stud-1-4-20/

I've got all the parts ready to go, just haven't put it together yet. I am super eager to give it a try and see if it makes a difference. If not, I'll have to blow up the cabinet. Seems like the logical next step.
 
If these are games with switching power supplies, jumper FG to logic GND.
 
I have a similar problem with a multi gun cabinet that I am working on.

In my case, the lines got worse as I added games to the cabinet. And they didn't exist on all games.

I am fairly certain that my power distribution system was terribly designed (by me...), so I have now ordered up a whole new host of materials to completely rebuild that portion of the cabinet.

If yours is like mine, then I think it's a ground loop. Basically your current has more than one path to ground, and due to the difference in resistance in each, can end up inducing unwanted current and noise in the wrong places. Would make sense that some solved it by removing the ground on the monitor frame, which is basically the same as removing a potential ground loop.

I ended up buying a book on the subject and after reading the book realized I'm dumber than a lot of folks out there (book was basically written for engineers lol, wasn't easy to follow). But I did take away a pretty big design tip. Any time you can, you want to use what they refer to as a "star" configuration for your grounding (actually it recommends to mirror your voltage distribution to however your ground is set up, so I suppose in a sense to your voltages too). So find a place that you can basically run all your grounds to a single point, which should then be as short a distance as physically possible to the earth ground connection of the machine. To say it a different way, hold your hand out in front of you and spread out your fingers. Your fingers and thumb are each a ground wire in the system, all coming together and connecting at your palm, and then your wrist/arm is the cabinet earth ground connection that goes out to the wall.

I ended up ordering a bunch of these to create this:

https://www.waytekwire.com/item/47217/Junction-Block-Stud-1-4-20/

I've got all the parts ready to go, just haven't put it together yet. I am super eager to give it a try and see if it makes a difference. If not, I'll have to blow up the cabinet. Seems like the logical next step.

Would you mind posting a picture of the wiring in your cab?
 
replace or recap your game PCB power supply.

you are seeing AC interference getting to the monitor.

removing the grounds from monitors will not hurt their normal operation.
when they are tested on a bench or at the factory, just using an ISO there is no ground going to them and they run for hours or days.

yes it is a quick band-aid until you can swap out or recap the PS.
i do it because i don't have time at events or the caps on hand at that time to re-cap some oddball PS's

If these are games with switching power supplies, jumper FG to logic GND.

all that does is band-aid the issue, the PS is still bad and needs replaced or recapped.

if it is repaired correctly there is no need for this.

Peace
Buffett
 
all that does is band-aid the issue, the PS is still bad and needs replaced or recapped.

That is not what the purpose of the jumper would be. A switcher on it's way out needs to be dealt with, in which case that jumper wouldn't fix anything. My comment also only applies to games using switchers, obviously. Midway games typically came with those jumpers factory-installed.
 
Most of these games I have already replaced the switchers with brand new ones. The interference was exactly the same before and after.
 
try removing ALL the grounds as a test from the monitor.

if it goes away then your still getting AC interference from somewhere.

Peace
Buffett
 
Would you mind posting a picture of the wiring in your cab?

Well I've taken it apart, but I think I have some pictures of the box when I first made it. I can post that.

For what it's worth, my power supplies are all brand new as well.

I DID notice that one of them is SUPER touchy on the 5v adjustment knob. Like even a slight bump will jump the voltage all over the place. Might replace that one.
 
That is not what the purpose of the jumper would be. A switcher on it's way out needs to be dealt with, in which case that jumper wouldn't fix anything. My comment also only applies to games using switchers, obviously. Midway games typically came with those jumpers factory-installed.

this.

this only really happens on the screw terminal power supplies anyway. doesn't matter if they're 20 years old or brand new. it usually only happens on monitors with switching mode power supplies built in (see: don't require isolation transformers)

upon doing so you can earth ground the monitor 60 times over and the ghosting should be gone.
 
Simple Test

Use a UPS plugged into the wall and the game plugged into the UPS.
A UPS uses a battery to filter power...
If you see interference then, it's the game PS, monitor, etc.
 
Use a UPS plugged into the wall and the game plugged into the UPS.
A UPS uses a battery to filter power...
If you see interference then, it's the game PS, monitor, etc.

I don't think it actually works that way.

The battery isn't active until it's needed.

And I'd be scared to plug a game into a UPS that was supplying battery power to it because most will be providing square wave approximations of the sine wave they'll get from the wall.

I damaged a brand-new Yamaha A/V receiver years back by plugging it into an APC UPS and switching it to battery power so I don't experiment with that anymore. :)

If you wanted to go that route, you could try a nice line conditioner.

Edit: Oooh, this is pretty interesting. If you have a Sega XY game and are concerned about the (over) supply of voltage from the wall blowing up your G08, try one of these:

https://www.walmart.com/ip/APC-LE12...online&wl12=13213504&wl13=&veh=sem#about-item

You can set it to deliver 110V!
 
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