Can't focus Double Dragon

GoneMad

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Just lately my DD starting acting strange. I cant remember if this one has the K4903 or the G07. I will have to go look. Anyway, it has just been recapped and was working great. Then I turned it on the other day and noticed the screen quite blurry. I turn the focus on the flyback all the way and this is about as clear as I can get it. I'm sure this is a monitor issue.
 

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Does the focus change at all when adjusting the pot? If not, I suspect your focus wire has come loose from the neckboard.

I doubt you have a G07 or 4900 in there, if it's original. DD usually came with a K7000. If that's the case, check your flyback knobs. If they're white, there's a good chance your flyback is on its way out.

(risky) Leave the monitor on for a few hours. Does the focus change (drift)? If it does, you have flyback issues.

I have a K7000 in a JAMMA cab in my lineup that turns on blurry, but then locks in after about 15 minutes. I'm sure the fly is getting weak, it's a white knob one. The game gets so little use that I figure when it goes, I'll do a rebuild kit on it. I already have a spare chassis standing by.
 
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When I adjust the knob, the focus does change. I will leave it on for a while and see what goes on. Maybe not for a couple hours though, but I do have a few things to do around the cabs today, so I'll keep an eye on it. I guess this should have been in the monitor section, but I wasn't quite sure, if it was 100% monitor related.
 
When I adjust the knob, the focus does change. I will leave it on for a while and see what goes on.
I wouldn't... Check to see what kind of chassis it is. If it's a K7000 with the white knobs on the flyback, go directly to replacing the flyback, do not pass go, do not collect 200 volts.

I guess this should have been in the monitor section, but I wasn't quite sure, if it was 100% monitor related.

It's the monitor.

-Ian
 
I wouldn't... Check to see what kind of chassis it is. If it's a K7000 with the white knobs on the flyback, go directly to replacing the flyback, do not pass go, do not collect 200 volts.




-Ian

It's the K4903. Here's a quick pic I just took. I never powered it back up, just took a shot. So it's the flyback I should replace?
 

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It's the K4903. Here's a quick pic I just took. I never powered it back up, just took a shot. So it's the flyback I should replace?

Yeah, the flyback not only generates the focus voltage, but it also contains the voltage divider circuit (the thing with the knobs on it) that allows you to adjust it. As the pots fail, the voltage drifts. Work the pot back and forth several times, see if you can get it to clear up. After the monitor is on for a while, you might see it get better. That's a sure sign you need a flyback.

I cautioned against running a faulty K7000 because those flybacks are well known for failing, and arcing, and taking out other things (voltage regulator, etc). I replace one of those at the first sign of trouble, or if I see any cracks in the housing.

4900 flybacks are usually very reliable, but I've seen a couple of bad ones. Fortunately, they're now available new - Chad at ArcadeCup has them.

-Ian
 
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