If you’ve worked on many arcade games, you might have come across a problem where your picture does not fill up the entirety of your screen even after you’ve tried multiple potentiometer adjustments. It could be that this problem is related to a part on your monitor chassis called the horizontal width coil. In this post, we will discuss how to adjust the horizontal width coil so that the picture fills your screen on your arcade monitor.

Adjusting The Horizontal Width Coil

Before you begin, we highly recommend purchasing a plastic or non-conductive alignment tool kit. These kits come with plastic tools that are specifically used to adjust these kinds of parts. You can use an Allen wrench to adjust the horizontal width coil, however, there are many down sides to doing this. For one, an Allen wrench generates a lot of torque that could cause your coil to crack or break. Also, you must have the game off while you are using the Allen wrench to adjust the coil. If the game is on when doing this the Allen wrench will heat up and can burn your hands not to mention that you will be navigating around some very high voltage areas with a piece of metal in your hand. Take our recommendation and purchase a plastic or non-conductive alignment tool kit.

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Please make sure to be careful around your chassis if you are attempting to adjust the coil while the game is on. Should you make contact with any high voltage areas on your chassis you could receive a bad shock. Be very cautious at all times when attempting this process. Also, it’s a good idea to set up a mirror in a position where you can the results that are caused from your adjustment.

Now that you have the correct tools and setup, it is time to adjust the horizontal width coil. Take your alignment tool and carefully place it into the coil and attempt to turn it. You may need to turn it clockwise and counter-clockwise a couple of times to loosen it up. Try not to force it too hard as too much torque even with the alignment tool can break your coil. If you cannot get it to turn or do not see a change in your monitor you might try leaving the monitor on for about an hour and retrying this process. This should cause the coil to heat up making it more easy to adjust.

If you have tried the techniques we’ve mentioned and you still do not see the changes you want, you could have more of a capacitor problem than a horizontal width coil problem. Look around your coil and see if you can find any polypropylene capacitors. These capacitors typically look like rather large pieces of Chiclets chewing gum and also control the picture width. Try replacing these capacitors to see if it changes your picture. You could also try checking your B+ voltage adjustment on your chassis. If the value of it is incorrect (it should be 120 VDC on most monitors) then this could also cause some picture size issues.

A Polypropylene Capacitor

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If you deal with enough arcade games you will eventually come across this problem where the picture does not fill up the entirety of your screen. Knowing how to adjust the horizontal width coil as well as the other measures we described should help you greatly in solving these issues in the future. As always, please leave any questions or suggestions in the comments section below.