A few questions about a Kortek KTN 20 chassis

[ckong]

I have an old neo geo cab with a 19" monitor in it and with a Kortek KTN 20 chassis:



I have a few questions about it:

A. what are the two black switches for (Marked 'A' in the picture)? The left is marked 'HS' and the right is marked 'VS'. They both can be set to NEGA(tive) or POSI(tive). At the moment they are both switched to NEGA.

B. There is a white pot ('B' in the picture) marked 'H-position'. I can turn it only a few milimeters to th left or right, and when I turn it I don't see anything changing on the monitor screen. What is it for?

C. There is another white pot ('C' in the picture) which on my chassis is set fixed with hot glue. What is it for?

D. I have a problem with the Horizontal width of the picture on the monitor screen, I mean it's to wide and I lose about 1 or 2 cm. of the image on the left side and right side of the screen. I can't get it more narrow without a lot of distortion. I tried to adjust it with the 'H-SUB POSI' pot on the breakout PCB, but without any luck. What can be the cause of this? (The Vertikal height is OK and can be adjusted fine).

[Ken Layton]

"A" is the sync signal select switches. This chassis can accept positive or negative sync signals. Just set them BOTH to the same setting. If your gameboard generates negative sync (most are) then both switches should be set to negative.

"B" adjusts the horizontal positioning of the image on the face of the tube. Normally a trimpot like that should turn 180 degrees. However, if yours only turns a little bit it may either be glued internally or has gone bad.

"C" is probably the X-Ray safety shutdown pot which was adjusted at the factory. Do not attempt to adjust it. That's why it's glued.

"D" there is a width coil to the left of the flyback. Use that to adjust the width. It requires special plastic tools (available at Radio Shack). NEVER USE METAL TOOLS OR ALLEN WRENCHES TO ADJUST WIDTH COILS.

[ckong]

"D" there is a width coil to the left of the flyback. Use that to adjust the width. It requires special plastic tools (available at Radio Shack). NEVER USE METAL TOOLS OR ALLEN WRENCHES TO ADJUST WIDTH COILS.

Thanks for the very informative answers and the warning. Be assured that I will not try to do something I'm not sure about. So I first will read something more about horizontal width coil adjustments. (for instance here is an interesting article which you probably already read: http://homearcade.org/BBBB/wc.html

[ckong]

OK, I found the horizontal width coil on my chassis, at least I think I did. Is it the part next to 'E' in the picture below?



If so, how can I adjust it? I mean, it's not in an upright position, but laying flat down, at one end there is some big round black 'thing' with a white spot, at the other end there is the metal protection shield (which end do I have to reach anyway?). Taken the high voltage risks in mind I don't want to disassemble all kind of things or fiddle around in a tight and crowded space.

And I also saw another pot, marked 'F' in the picture, which on my chassis is secured with hot glue. What is it for?

[Ken Layton]

"F" is the B+ power supply adjustment. Don't touch it.

Your particular width coil appears to adjust from the side of the flyback cage next to the focus and screen controls. Your picture isn't very good since I can't see the opening for the focus and screen adjustments. I'm guessing there is a hole in the aluminum frame to stick the plastic adjusting tool in there to turn the width coil.

[ckong]

The picture above is not a picture I made, I got it from Jomac.

But you're right, there is a hole, as you can see in the picture below (made by me, the picture I mean).



Now I need to find the right tool in a shop somewhere in The Netherlands to adjust the coil   How is this tool called?

thanks for your help, and here is my final question: what are the two pots at the questionmark for?  I won't turn them, there is a high voltage warning very nereby these pots 

[Ken Layton]

Top one is focus and bottom one is screen adjustment.

The tool you need is called plastic hex tv alignment tool. They come in different diameters and most are metric.

www.radioshack.com sells them and I think they have a picture of them too.

Check out item # 64-2220 or 64-2230.

[ckong]

Thanks, found the tool. 

Edit: after I found out that shipping costs to The Netherlands are pretty high for such a tool , I decided to make my own tool. I very carefully used a metal allen wrench just to measure the size of the hole in the coil, and then I carved a little tool out  of some plastic thin stick I had 

Then I carefully adjusted the horizontal width coil (in my case about 12 half turns anti-clockwise, if I did more the screen become more wide again) and now I narrowed the screen so that I have an almost complete picture (only still a few milimeters loss on both sides, who cares).