Arcade monitor problem

[trenal]

Hey, I have a 6 slot original neo geo machine. Ive recently begun to notice a small problem with this machines monitor.

Ive got a 26" zenith tube with a Kortek chassis. The minor problem I've been having is that certain actions in games cause the monitor to distort, most noticably when 'flashes' of animation come on the screen other areas of the monitor get affected for short periods of times (you have to look closely) eg when one side of the screen has P2 START flashing the other side of the screen "distorts" according to the flash.

So certain games can really be affected by this but other games arent. Again for example in a game like super sidekicks you don't notice anything where as in puzzle bobble when you "burst" a bubble the resulting flash of brightness distorts all the image in the vicinity (tough to explain without a video clip of it, like the image slightly collapses inward then outward) This took me a while to pick up on and now I notice it all the time and I know other machines I've used didint do this so there is a problem somewhere.

I've attempted to raise the +5v from the power supply with no change and I've also just installed a cap kit which fixed some minor screen problems I was also having such as the top of the screen folding in, but it didnt fix the problem mentioned above.

Im yet to try a different power supply or different gameboard in an attempt to narrow down the problem but I doubt either of these 2 can cause the problem I'm having

Any ideas would be appreciated.

Trenal.

[Ken Layton]

Did you do the full capkit or only change 3 or 4 caps? A typical Kortek capkit contains 22 capacitors plus two resistors for the power supply.

[trenal]

Thanks for the quick reply Ken.

I changed out all 22 electrolytical capacitors as described by the user manual, I didnt get an official cap kit from anywhwere but bought the parts separately from an electronics store. I couldnt locate an official cap kit for this chassis but managed to find all the ones I thought I needed.

Are 2 resistors also part of an offical cap kit? If there are any other known parts that go bad on the Kortek chassis please let me know.

Thanks

Trenal.

[Ken Layton]

There are several versions of the Kortek. If yours has 68k 1/4 watt resistors at locations R608 and R609 in the power supply section they should be replaced with like values. I've found that most of the time Zanen Electronics' kit # 501 covers most Kortek models and so does kit 520. Kortek monitors were sold under several names here in the USA like Imperial, Wico Videomaster, Penn-Ray Sutra, Sharp image, etc.

It's possible the Zenith picture tube is starting to go bad. Wells-Gardner had such a problem with them that they stopped using them and went to Phillips and Samsung as their main picture tube suppliers.

[trenal]

According to my manual:
R608 - 8.2k 1/4 W
R609 - 8.2k 1/4 W

I must have a different revision board to the one your familiar with.

[Ken Layton]

Sounds like you got the Sharp Image version (SI-327 perhaps) which would use kit 608 from Zanen.

Might be a good idea to contact tech support at Sharp Image (www.sharpimage.net) and describe your problem to them. I don't run into many Sharp Image monitors (many used grade "B" picture tubes, the bottom of the barrel).

[trenal]

OK, thanks for your help ill check out the sharp image website but as you suggested its likely to be that the tube could be on its last legs. Ill also get in touch with zanen about the kit.

Locally (I'm in Australia) i just cant find many techs or proffessionals (probably like yourself, Ken) willing to help out with old arcade monitors, hopefully ill have better luck when i contact sharp image.

[trenal]

Hey,

While im still having monitor problems weeks after my first post on this topic, Ive also just realised that my monitor flashing/bouncing problems arent there for the first 30-40 seconds of my cabinet being turned on. They only start occurring after this time.

Because of this im not sure if the tube is the problem, Any ideas? I havent tried a new arcade PSU as yet so I was wondering if its possible the arcade PSU can cause these problems?