Is this what you call a hum bar?

TheDrewster

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Im beginning to notice a slight wave going through my Galaxian monitor. It is visible when you stare at it, even more so with the convergence grid displayed. Is this what people have been referring to as the hum bar?
 
The hum bar looks like a moving vertical (in a Galaxian cab) bar that goes from left to right, distorting the image. Similar to a wave or ripple on a pond.

It's typically caused by a dirty edge connector, or especially in Midway games, dirty or loose fuse holders. Those old brass holders are usually shot; you can get replacements at Radio Shack that will screw right in place using the same screws as the originals, just solder one wire at a time to keep them in order.

If your game has the RF filter board on the edge connector, take it off and plug the harness directly into the game PCB, also make sure that edge connector is clean on both sides. Usually a good sized eraser will safely remove any oxidation on that connector, avoid sandpaper.

Between those fixes you should see the 60 hz hum bar disappear.
 
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