Posted by Drew Rudman on May 16, 2013

Centipede Monitor Sync

This issue has plagued my Atari Centipede system previously. Whenever you turn the system on, the screen will be scrambled like the following:

Centipede Scrambled

The demo game play is visible but scrambled. You can “resync” the monitor with a quick on-off-on flick of the power switch:


The left side of the screen is also distorted.

I decided to contact Jonathan Leung of regarding the issue. Jonathan has produced a series of great YouTube tutorials on how to troubleshoot and repair arcade games. He was very helpful via email and suggested checking out an article written by the great Bob Roberts on dealing with a slanted picture on a Wells/Gardner K4600 monitor. To tackle that, I needed to order a plastic screwdriver which I found in this Universal Color TV Alignment Tool Kit recommended by Jonathan. I placed an order for that and will tackle the issue once it arrives.

As for the distortion on the left side of the screen, Jonathan suggested that it could be fixed by adjusting the horizontal hold, the vertical hold, the horizontal metal pot Bob talks about in the slanted picture article. If that did not resolve the issue, he also knows of a mod that can be done to correct the curl and will look that up if it is needed.

The Universal Color TV Alignment tool arrived from Suzo-Happ and started in on trying to adjust the horizontal hold and horizontal adjustment pots as detailed in Bob Robert’s article. The centipede monitor is oriented vertically and Bob’s article discusses the monitor in a horizontal orientation, but the approach is the same. By adjusting both the Horizontal Hold and the Horizontal Adjustment pots:


I was able to pretty easily “unslant” the monitor image. It was a little tricky feeding the plastic screwdriver through the indicated hole in the metal chassis protecting the monitor PCB board, but with a little care, the tools from the Universal Color TV Alignment kit did the trick:


To address the “curl” I continued to see on the left side of the screen, I continued to manipulate the Horizontal and Vertical Holds and the Horizontal Adjustment. The best I could arrive at is still slightly curled:


I reached out to Jonathan to get additional information on the modification he knows of to address the curl, but I have a feeling it might not be worth the effort. The image looks pretty solid.

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