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Kortek 25" Monitor Contrast issue
Posted: May-18-2015 9:36 AM
Join Date:Dec-31-2014
Post: 1

Hi everyone,

First time poster and still pretty new to the hobby, but running into some problems with a monitor I have. I recently picked up a Neo Geo 2 slot system with a Kortek 25" monitor. There is no model number listed anywhere on it, but Bob Roberts said after looking at the manual that it's essentially a K7000 clone. I scanned the manual and sent it to the ARCade ARChive, and they posted it here: http://arcarc.xmission.com/PDF_Monitors/Kortek_Manual.pdf

So to the issue, when I first picked up the monitor it had a vertical collapse issue going on. Buddy and I worked through it and followed Randy Fromm's flow chart based on the K7000 and it led us to a resistor being bad. Replaced R91 and it caught fire, so the flow chart alluded to IC 2 or IC 3 needing replaced. I bought both of those and soldered in the new ones, replaced R91 again and I have a picture.

However, the contrast was bad and barely visible in a lit garage. Buddy of mine accidentally set something on the remote monitor control and it broke the contrast pot, so I replaced that with a new pot from Bob Roberts. I recapped the monitor using a K7000 cap kit and the picture is better, but still not great. I was also able to control the contrast using the new pot BRIEFLY but then I lost it.

Reading the manual, IC 1 shows a contrast amp inside of it, so I figured I'd replace that all together and see if I could get some control back. Fired it up again and still no control via the contrast pot.

Any ideas on what could have happened? Is it at all possible a bad or faulty IC 1 threw the good pot that I replaced? I have not tried replacing the pot yet again.

The pot measures fine on a multimeter set to 20k, goes from almost 0 to 9.something as I turn it. I also tested all the circuits on the remote controller for continuity and it appears good. I touched up a few solder joints on the controller just in case, but still no dice.

I'm at a loss for how to adjust my contrast now. If I could do that, this monitor would be absolutely dialed in.

Thanks for any help you guys might have.

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