Checking And Replacing A Power Supply

Checking And Replacing A Power Supply

Power supplies are a great starting point if you are trying to troubleshoot problems with your arcade machine. Bad voltage can cause a variety of problems that can sometimes be mistaken for a bad board. In this post, we’ll talk about how to check a power supply for the correct voltage as well as how to replace a power supply should it go out.

Checking And Replacing A Power Supply

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Before we get started, it’s a good idea to unplug your monitor and board from the power supply. If our power supply is bad, we don’t want it to damage anything in our cabinet. Also, if the power cord on your arcade game is missing the ground prong, you should think about replacing it. The ground prong gives you protection against shocks that might occur due to electrical issues. With that said, let’s plug in your arcade game, turn the power switch on and get started.

In order to check the voltage on your power supply, you will need to use a multimeter. Multimeters have several modes; some of which we have talked about in previous posts. The two modes we are going to talk about here are Alternating Current (AC) voltage (VAC) and Direct Current (DC) voltage (VDC). Some multimeters have several different settings for AC voltage and DC voltage. You always want to set the multimeter on the first voltage setting that is greater than what you are trying to test. For instance, if you’re trying to test the AC voltage coming out of a plug, a good setting would be 200 VAC as AC voltage in the United States is usually between 110 and 130 VAC.

With our multimeter now set to VAC, let’s check the AC voltage coming into our power supply. Place one of your multimeter leads on each of the terminals marked AC on your power supply. As we stated before, you should read somewhere around 120 VAC. If your multimeter does not read around 120 VAC, it’s time to start tracing down your wiring to see what the problem is. A reading of 0 VAC is a good indication that there is no AC voltage going to your power supply. Check the connection between your main arcade power cord and your power supply to find the problem. If your voltage is not around 120 VAC, check your wall plug to make sure it is reading correctly. If it reads correctly, check for items inside your arcade cabinet that might be causing power issues.

Now that we have checked your AC voltage and verified that it was correct, we can now test your DC voltage. DC voltage is what powers your board, controls, and coin door lights among other things. In order to test our DC voltage, we need to set our multimeter to VDC. We will be checking voltages around 5 and 12 VDC so a good setting on your multimeter would be 20 VDC. Once you have your multimeter set, it’s time to test our 5 VDC. Place your black lead on the common (or ground) terminal and place your red lead on the +5 VDC terminal. You should get a reading that’s around 5 VDC. Keep that reading in mind while we test the 12 VDC. While keeping your black lead on the common (or ground), move the red lead to the +12 VDC terminal and keep this number in mind as well.

After reading the 5 VDC and 12 VDC, you might realize that these numbers are a little bit higher or lower than what they are suppose to be. You might have noticed a knob on the power supply. This knob controls the DC voltage output. Turning the knob right or left can increase or decrease the amount of DC voltage coming out of the power supply. Turn this knob to the right or left and test your 5 VDC and 12 VDC to see if they are closer to the correct voltage than before. If you are coordinated, you can test the voltage while turning the knob but either way should be fine. Once you are satisfied with the DC voltage output, turn the arcade game off, plug in your board and turn it back on.

If you try and turn the knob but you can’t seem to get both the 5 VDC and 12 VDC close enough then you might need a new power supply. You can buy power supplies from our favorite parts distributor: Replacing a power supply is easy. First, make sure the game is unplugged. Then, remove the wires from the terminals on the existing power supply and place them on the matching terminals of the new power supply. You might want to label the wires as you take them off so you can make sure you put them on the correct terminals of the new power supply. Placing the wrong voltage on the wrong terminal can have dire consequences for your arcade game! Once you have done this, you have successfully replaced a power supply.

It is important to note that some power supplies today don’t have terminals and instead are connected to the board by a Molex connector. If this is the case with your power supply, you can still check your DC voltage by using the black wire as your common (or ground) wire, the red wire as your 5 VDC, and the yellow wire as your 12 VDC. Just follow the exact same steps above except put your leads into the connector instead of on the terminals. You might also notice that your power supply has a -5 VDC. While this isn’t used much in newer games, you can still check it. Just use the same technique that we used with the 5 VDC and 12 VDC terminals. The -5 VDC is usually indicated by a white wire on a Molex connected power supply.

Many strange problems that you encounter in arcade repair can center around the power supply. It’s always a good place to start if you’re not sure what the problem could be. Please let us know if you have any questions or suggestions by leaving some comments below.

  1. Avatar


    Great video. I still have some issues with my power supply though.

    I’m using a PC power supply as testing power supply on my workbench. When I measure the voltage of the +5V line, it shows around 5.3V, which might be a bit high, but still rather acceptable.

    However, if I connect a PCB and measure the +5V line again, it shows about 3.5V. Is this a normal thing? Could this be the reason why some of my PCBs aren’t working?

    Thanks in advance and greetings from Belgium!

  2. Avatar
    Jonathan Leung


    No, it is not normal for a good power supply to drop that much on the +5 VDC under a load. This could definitely be the reason why some of your PCBs aren’t working. We highly recommend trying a different power supply, preferably one that is for arcade games. Remember that if the board is not receiving the correct voltage it will not work properly.

    Thanks for your question and watch for more posts.

  3. Avatar
    paul juray

    good video,i have a super pacman with an old linear power supply.can you do a video showing how to update to a new power supply? thankyou

  4. Avatar
    Jonathan Leung


    Thanks for your suggestion. We get this request quite a bit so expect a post and video on it very soon. If you don’t want to wait till then, check out a power supply conversion kit from Arcadeshop Amusements. This kit makes it very easy to install a switching power supply in your older arcade games.

    Visit the Arcadeshop Amusements page at and do a search for “Super Pac-Man power supply conversion kit” without the quotes for more information. We bought a kit for our Qix a while back and it worked like a champ. The kit usually comes with a little board, a new switching power supply and some instructions.

    You can, of course, do it without the kit but it requires a lot more time and going through wiring. This kit will save you a lot of time and possibly a headache. It’s pretty much a plug and play solution.

    Thanks for you interest and good luck with your project.

  5. Avatar
    Jonathan Leung

    We received an email question about a Point Blank arcade machine that does not turn on at all. Here was our response:

    The best place to start on this problem is to make sure you have power coming in from the wall. If you saw the video on Checking And Replacing A Power Supply then you should be familiar with using a multimeter. Take a multimeter, switch it to VAC mode and check the AC voltage coming into the power supply. It should read around 115, if it’s a little high or a little low that’s fine.

    If you are getting good AC readings, check your DC voltage. There should be slots on the power supply for 12 VDC and 5 VDC. These are typically indicated by yellow wires and red wires respectively. Switch your multimeter to VDC and check these slots. If the voltage is too high or too low, use the adjustment knob to change it. If you get no voltage then you probably have a bad power supply.

    Now this problem could be indicative of a bad board or bad monitor. If you check your power supply and everything seems good you might move on to some of our other videos on monitors. Thanks for watching our videos and good luck with your repair.

  6. Avatar
    Michael Cruz

    I have a have a Neo Geo that works ok for most os the time,sometimes it ,goes to verticle lines. My buddy who works on these things looked at it and said I needed a new power supply as my 5v was too high at 5.5 volts.My 12v was just over 12. Someone converted this unit to a peter chow power supply, so I bought the same one to replace it. I can adjust it to 5.1 volts, but the 12v won’t come lower than 15.2 volts. I assume this is a bad power supply. The problem is the samet, except it’s only good for about two minute before it goes to verticle lines.Should I go back to a HD pc type power supply?

  7. Avatar
    Jonathan Leung


    We would say that your old power supply was is pretty good shape and could probably be put back in place of the new one. This problem sounds more like a monitor issue. We would definitely check the wiring going from your PCB to your monitor and maybe tap on you monitor frame with the game on to see if it generates the vertical lines you’ve described. If you get the vertical lines, check for cold solder joints on your chassis.

    We have also featured your question on episode 3 of our Q&A podcast. Please listen to it for more of our thoughts on your issue. Thank you for your question and good luck with your repair.

  8. Avatar

    hi guys, just discovered your website. excellent info you have here. anyway, ive got a switching power supply for arcade use, but its +24, +24, GND, GND, FG, AC(L), AC(N).

    my question is, how do i wire up this power supply since there are no 12v or 5v??

    thanks guys.

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    Hi, I’m running a Neo geo 1-slot through a cabinet, and it works perfectly, except sometimes, often when the game resets in attract mode, the picture goes off, with the sound/game still running fine, and only comes back on again when I unplug the whole cabinet and then plug it back in. Do you think this is a power issue? The cutout also happens when switching between the main game and continue screen, or during the intro of Last Blade (which is a bit visually complex). The MVS and cartridges all work perfectly, as I’ve had them running in another cab for hours at a time.

    Any help on this would be great, thanks!

  10. Avatar
    Jonathan Leung


    We are curious as to what arcade game this is going into. Some of the newer style games use 24 VDC but typically have the 12 VDC and 5 VDC included as well. While we have never seen an arcade game that just uses 24 VDC, it is very possible that you have one in your possession. We recommend locating the pinouts for this game to see if they show the 24 VDC line and where it goes on the harness.

    It is also possible that someone installed the wrong power supply in your game. Should you need a new power supply, we recommend a standard switching power supply from These are very similar to the one we use in our Checking And Replacing A Power Supply post. If you buy one and follow the instructions there you should be fine.

    We have also featured your question on episode 11 of our Q&A podcast. Please listen to it for more of our thoughts on your question. Thank you for your question and keep us updated on your progress.

  11. Avatar
    Jonathan Leung


    You asked us if this is a power issue and it sure sounds like one. We recommend checking your 5 VDC and 12 VDC on your power supply to make sure that both are giving you the correct voltages. You can also try checking the power at the board on the JAMMA harness to see if you’re getting the same 5 VDC and 12 VDC there. Keep in mind that it’s better to be a little high on these voltages than low so make your adjustments accordingly. If you continue to have problems after you have adjusted the power supply then it might be time to look at your board for problems.

    We have also featured your question on episode 11 of our Q&A podcast. Please listen to it for more of our thoughts on your question. Thank you for your question and good luck with your repair.

  12. Avatar

    I have an area 51/maxforce. I replaced the disk drive since it was bad and the power supply sounded bad so I bought one from Happ. The power supply I bought reads the +5 around +5.5 and the +12 around +11.7. thats as good as it gets. this sounds to far out of range for me. Also according to the diagram on the power supply what should be positive is reading negative and negative is reading positive?????? I am lost…..any suggestions would be highly appreciated.


  13. Avatar
    Jonathan Leung


    Even though we might be able to get this power supply working, it’s disappointing to see how far out of range it is. We would recommend lowering the +5 VDC line down to about 5.1 and the +12 VDC line down to 11.5. If you cannot get the power supply in this range then you might need to contact Happ about getting a new one. As for the positive/negative readings, it could be that you have your black and red leads mixed up either during your test (the black should be on the ground) or hooked up to your multimeter wrong. I wouldn’t worry too much about it, just see if you can get the voltages around where we recommend.

    We have also featured your question on episode 23 of our Q&A podcast. Please listen to it for more of our thoughts on your question. Thank you for your question and good luck with your repair.

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