Question Looking for some help with screen interference being caused by ATX PSU.

[purbeast0]

I want to preface this post by saying that this is dealing with my arcade cabinet and a JAMMA game.

That said, I have a couple games that require a separate ATX PSU to power the game. Most JAMMA games are just a board (or two connected) that plug into the JAMMA harness and the game just plays like that.

But I have a couple where the game is basically a computer running a linux drive that boots into the game and then there is an I/O board that connects to it and the JAMMA harness connects to that.

Those games are using some standard PC hardware. It's just a normal motherboard, cpu, RAM, and ATX PSU.

I recently got 2 of these games and ran out and got 2 ATX PSU's from Microcenter since I assumed any old ATX PSU would be fine. Here is the exact PSU that I got.

Solid Gear SDGR-400BX 400W ATX Non-Modular Power Supply - Micro Center

Get it now! Affordable and Reliable Solid Gear Basix SDGR-400BX deliver efficiency 400W power to your system. It provides efficiency and affordable power to your system. It also produce better airflow. This entry level power supply cosumes less energy.

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Here is a pic of what the one game in question looks like all mounted.

Upon setting it all up I quickly noticed there was screen interference that was bothersome. I'd see some 45 degree lines scroll across the pic when it was darker and the picture looked "fuzzy". I took a video but it was pretty hard to see it in the video.

I then decided to try out the PSU in my desktop PC. It's an old Antec NeoPower 550. And wouldn't you know it - immediately the interference was gone. I mean it was 100% gone. I then took the PSU out of my desktop case just in case and tried it that way, and again, there was absolutely no screen interference.

So that narrowed it down to the PSU as the 100% reason for the interference.

I have taken some ground readings with my multimeter and the new PSU's I got, when I take the reading from the ground pin on the main plug of the PSU to the housing on the PSU, I get a reading of 0.1ohm. If I do a reading from any of the plugs that plug into the HDD and either the housing or the ground pin of the main plug, I get a reading of 4.5ohm on one and then 5.0ohm on the other. And again these are both of the PSU's I got from Microcenter.

If I take the reading from the PSU that is in my desktop, it looks like the housing isn't even conductive as I get no readings at all. If I take a reading from the ground pin on the main plug to a ground pin on one of the HDD plugs, then I get a reading of 0.1ohm. So that right there is much different than the reading on the other PSU.

I don't know much about PSU's and electricity in general at all, but I took those readings for people who asked about it on the arcade forum I post on. I thought I'd give it a shot here too and see if anyone has any ideas.

One thing to keep in mind as well is that on the ATX PSU's that I bought from Microcenter, on both of them I have messed with the wiring a little bit because I wired them to a relay so that they power on as soon as the arcade machine powers on and then power off once the machine is off. To do that I had to splice into a ground wire on the PSU as well as the green switch wire on the PSU and attach them to the relay. All of that is working fine.

HOWEVER, then I did these readings up above, I had removed the relay from the equation and I soldered the wires back together. I took as many variables out of the equation to see if I could get rid of the interference but it never happened. But right now, I have all of the wires connected and the ground wire and green switch wire I had spliced into, I now have them soldered back together again. I bring that up because I am not sure if that could have any effect on the problems with screen interference I am having.

So does anyone have any ideas? Did I just get a crappy PSU? Is there anything I can do to fix this? I'm willing to open up the PSU and mess with stuff inside too if need be. I literally got one of the cheapest I could find because the game required 250w and this was 400w so I figured it would be just fine. The game works fine and everything, but the screen interference bothers me too much.

Thanks.

 

[Mr Evil]

Can you take a photo of the inside of the PSU, straight from above so all the components are visible? It sounds like they may have cut a few too many corners when making it.

 

[purbeast0]

Can you take a photo of the inside of the PSU, straight from above so all the components are visible? It sounds like they may have cut a few too many corners when making it.

Do you want me to take the metal casing off to do this? Or do you just mean so you can se through where the fan is?

 

[Mr Evil]

With the case off, to be able to see if they've done something like omit a mains filter.

 

[purbeast0]

With the case off, to be able to see if they've done something like omit a mains filter.

Here you go. This is from a few different angles. Let me know if you need a closer look at anything.

 

[Mr Evil]

In the first photo, you can see some empty positions for components on the right-hand edge of the PCB. There should be a mains filter there, consisting of some capacitors and inductors. Cheap PSUs sometimes don't have these, as they cost money and aren't strictly required for the PSU to physically function. If they aren't there though, then there's nothing stopping the PSU from spewing horrible interference out over the wires into the rest of the building.

It is possible to fix that, either by adding the missing components or inserting a self-contained filter somewher inline, but when the manufacturer clearly doesn't care about adhering to regulations, I wouldn't trust that they haven't also comprmised safety, and would just replace it.

 

[purbeast0]

In the first photo, you can see some empty positions for components on the right-hand edge of the PCB. There should be a mains filter there, consisting of some capacitors and inductors. Cheap PSUs sometimes don't have these, as they cost money and aren't strictly required for the PSU to physically function. If they aren't there though, then there's nothing stopping the PSU from spewing horrible interference out over the wires into the rest of the building.

It is possible to fix that, either by adding the missing components or inserting a self-contained filter somewher inline, but when the manufacturer clearly doesn't care about adhering to regulations, I wouldn't trust that they haven't also comprmised safety, and would just replace it.

Damn okay thanks for the input. So it sounds like there is no "simple" way to do this then huh. Is adding the missing components something simple or the filter? Like is it something I can buy cheap and just give it a try? Sounds like you don't recommend that route just because this looks like a cheap PSU that could have other issues.

Do you have any cheap ATX PSU you recommend? Again the requirement for this is 250w and I got this 400w thinking that would be enough and not knowing anything about this type of stuff. But I guess missing components is how the price was so cheap at $16 for it.

I have 2 of these and wonder if Microcenter will even take them back because I've spliced into the wires, even though I have them soldered back together. And I tossed one of the boxes long ago too lol.

Also one thing to keep in mind - this PSU will not be used too often. It only powers on when I play those specific games in my cabinet, and like realistically it won't be that long, especially not at a time. Like I'd be surprised if it was on for an hour at a time even when I did play it.

 

[purbeast0]

Also if I do return these and buy completely new ones, are there any specific things I should look for on the specs so that I don't run into this problem again?

EDIT:

They have been returned. Only other brand they had at Microcenter was a Powerspec and like 430w I think it was, for $45. I'm going to see if I can find something cheaper than that for sure and a name brand.

 

[Mr Evil]

Is adding the missing components something simple or the filter? Like is it something I can buy cheap and just give it a try? Sounds like you don't recommend that route just because this looks like a cheap PSU that could have other issues.

You can get IEC sockets that have filters built in which are not too expensive, and easy to fit. But indeed, I wouldn't bother trying.

Do you have any cheap ATX PSU you recommend?

are there any specific things I should look for on the specs so that I don't run into this problem again?

I don't buy enough PSUs to be able to recommend any in particular. There are some fairly reliable indicators of general quality:

• Anything with an 80+ certification is probably decent.
• Wide input voltage range, i.e. the input voltage is specified as something like "100-250V" rather than just "110V" or "240V" (but watch out that some PSUs may support two input voltages with a switch on the back, and that's not the same thing). Having such a flexible input takes some extra circuitry, and if the manufacturer has spent money to do so, they probably haven't cut too many corners.

Of course such things tend to drive the price up. Finding something for $15.99 that's any good is going to be difficult.

 

[purbeast0]

Thanks for the help.

I ended up just trying out this one since it was cheap and I could return it if it didn't work out.

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I got it today and there is absolutely zero screen interference. So I'll order another one for my other game.