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
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: therealbobroberts.net. 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.