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Author Topic: Kortek KTN-2001 CRT help -- weird sparklies onscreen  (Read 362 times)

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TapperP

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Kortek KTN-2001 CRT help -- weird sparklies onscreen
« on: March 19, 2019, 01:25:38 am »
Hey everyone,

I have a cab with a Kortek KTN-2001 monitor mounted vertically. It's a 19 inch standard res display.

It works well, but as I try different games on it, I started noticing weird dancing dots or patterns in some situations. They are actually always there, but most of the time it's faint enough that I don't notice them much, especially in classic 80's games.

Hard to describe, but here are some photos. See the bright dots in the color bars?  Please note they are NOT static, i.e. they dance like some sort of signal interference. Any idea what that is, and how it could maybe be fixed?



grantspain

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Re: Kortek KTN-2001 CRT help -- weird sparklies onscreen
« Reply #1 on: March 19, 2019, 01:49:21 am »
it could be earth related or possibly interference from marquee light
it could be a chassis fault but only seen that issue on hantarex polo and the brightness pot would not function either

disconnect marquee light first, next disconnect video signal and increase brightness so you get a raster to see if you still see the dots

TapperP

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Re: Kortek KTN-2001 CRT help -- weird sparklies onscreen
« Reply #2 on: March 20, 2019, 01:28:14 am »
grantspain, thanks for the reply. I will try that soon.

TapperP

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Re: Kortek KTN-2001 CRT help -- weird sparklies onscreen
« Reply #3 on: March 26, 2019, 12:11:07 am »
Some great news. I fixed it! Well, I greatly improved it at least.

So, it wasn't the marquee or anything like that. Very simply, one of the wires in the bundle with RGBH&V feeding from the JAMMA into the monitor chassis needed to be reseated and/or replaced.

I diagnosed it by carefully moving some wires around while my wife watched the screen. We noticed that when I moved the RGBEVH bundle the pattern would change, decrease or increase. So, I powered everything down, unseated the bundle from the monitor chassis, kinda straightened the connectors a little, and plugged it back in. Turned the cab back on, switched to a game on my Arpicade (Journey, blue screen) where you could see the pattern easily and it was GONE! =)

Now, having said that, after moving the cab back to its usual spot, when I looked at the color test display again the sparklies were still there, but much less pronounced. Basically I determined the white wire going into H (horizontal sync I guess) is a bit wonky. Even some minor movement when I moved the cab caused it to shift just enough to bring back the issue a little. So, at some point I will try replacing that one wire, which I think will fix the issue for good.

For now, I have it placed pretty well and see virtually zero sparklies or weird pattern noise as I did before.

Anyway, maybe someday this info will help someone else with a similar anomaly.
« Last Edit: March 26, 2019, 02:17:45 am by TapperP »