Trying to correctly align the convergence on an arcade monitor can be a frustrating experience especially for newcomers to arcade repair. It’s easy to get overwhelmed by the different ways to adjust convergence and the method that should be used for each type of convergence issue. In this post, James Dinndorf provides some helpful tips on adjusting the static and dynamic convergence of arcade monitors.
Let me start off by saying that I think it’s terrific what Arcade Repair Tips does for the arcade community, especially the newcomers. I myself, have been in the hobby for about 10 years now, first beginning with a Teenage Mutant Ninja Turtles restoration I bought from a local Skating Rink owner back when I was 21 years old. Now I’m up to about a dozen games, most of which are unfortunately in a storage unit in sub-zero climate or being stored at a friends house, as I am currently living in an apartment with my wife. With that said, it’s no surprise that the only two games in our apartment are Ms. Pac-man and the Megatouch. But I digress…
Here’s a little info that might help all of you out there with questions regarding monitor convergence. About two years ago I had my first in-depth experience with adjusting monitor convergence while working on restoring a two player T-MEK that has two 25″ monitors in it. One of the monitors, a Wells Gardner K7000 series, had a tube that I decided to replace with another (a K7191) that I had laying around in storage. It was a direct drop-in replacement, but unfortunately the convergence was noticeably off-set (at least to me). It was most noticeable with text such as scores, energy bars, player initials, etc. In other words, it drove me nuts. So I decided to tackle it.
Just a note before we begin. The monitor needs to be powered on during this process so that you can see the changes as they happen. In other words, you’ll be able to see the grid lines shift as you move the strips around under the yoke, against the tube. I had a buddy help by holding a mirror, but I also did some of it with the monitor outside of the cabinet. Please be VERY careful.
The first thing I did was check the manual and the K7000 describes it pretty well.
http://www.wellsgardner.com/pdf/Service/K7000.pdf (See Pages 6 and 7)
The first thing to note is that there are actually TWO types of convergence you need to adjust: static and dynamic. The first is static and is the easiest. This is where you use the convergence “rings” on the yoke. Using the game’s test screen, you have it display a grid pattern. Then, using two of the rings, you adjust the red and blue vertical lines until they overlap one another. Then you adjust the red and blue horizontal lines until they overlap. Once this is done, you adjust the rings in order to get the red and blue to overlap the green lines. The manual describes this very well and also has illustrations. This process is actually much simpler than most people think but it can be a little intimidating at first. Once done, you can use a marker to mark all of the rings for reference.
Next is the tricky part: dynamic convergence. Whereas “static” convergence covers mostly the inner area of the monitor/screen image, dynamic convergence covers the outer area, particular the edges. For example, if you had white text running across the entire monitor, you might notice that while the letters at the center of the screen look fine, the letters on the far left and right looked “ghosted” with shades of red, blue and green above and below. This is dynamic convergence that needs adjusting.
Adjusting this takes a TON of patience (as I found out) and the worst part is that a lot of it is simply trial and error. Whereas with static convergence, you use the rings on the yoke, dynamic convergence involves adjusting HOW the yoke rests on the tube itself. Again, the manual has a great description for a starting place. For myself, I loosened the yoke and played with it a bit, tilting and shifting it while looking at the crosshatch pattern on the monitor. Eventually you should be able to find a “sweet spot” where 75-90% of the edges and rest of the grid line up properly. This is where you want to set your rubber wedges (i.e. those little strips you see sticking out of the yoke) and mount them in place so the yoke rests there. Once that’s done it’s all fine tuning using the little strips to fix the corners and possibly some of the very fine edges. That’s how it worked for me.
After the static convergence, I played with the yoke with no wedges until I found that 85% of the grid looked good. At that point, I set the wedges in to hold it there. I actually used a few extra from another tube which gave me five wedges total. Then I made a bunch of homemade convergence strips (see the note at the bottom for description) and slid them underneath the yoke and against the tube. These strips are about 6-7 inches in length and the end with the blade attached is what slides under the yoke, with the other end sticking out. You will need to tape these in place or use some other form of (strong) adhesive so they stay in place. They’re used to correct specific small areas (i.e. a corner or edge) that require fine tuning. After a lot of patience, I finally got the corners looking good. I had to experiment a bit to get the very top edge to line up all the way, but got it after some time. I ended up constructing a convergence strip that used a piece of metal that was twice as long as the others. That for some reason did the trick.
In the end, the convergence on this thing was about as good as it gets and I’m really happy with it. I’ll admit that the area around the yoke looks terribly ugly as I used a ton of tape and adhesive to reinforce and hold all of the wedges and strips in place but the image is what really matters. Hopefully, this can provide some helpful guidance for those of you that want to adjust the convergence of their monitors but are too intimidated to try especially in this era where CRTs are at an all time scarcity.
NOTE: To make homemade convergence strips, you can simply go to your local hardware store. Buy a cheap razor blade, preferably one that has a long blade that you press up, notch by notch. Also buy some thin but solid cardboard to use for the strip itself. I bought a cheap yard sign for this. This should cost less than $10. All you have to do is carefully break off a piece of the razor blade about the size of a dime. Cut a small strip of cardboard and attach the piece of razor blade to the cardboard strip using electrical (or magnetic) tape. That’s all. You can experiment with the size of the piece of razor blade you use on each strip. Sometimes I found I needed more or less depending on where I was placing the strips.