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Having serious Jaguar video issues!!! PLEASE HELP


mwolf

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Hey everyone! I’m hoping someone out there has an idea of how to fix my Atari Jaguar. Other people have faced the same issues as shown in previous posts but it doesn’t seem anybody’s documented a fix. I’m a huge jag fanatic and this is my 3rd system, my original purchased in ‘95. I’m dying to figure this out. The screen will produced 5-6 black dotted lines vertically on the screen, a couple inches apart. It doesn’t begin to show to show up until about 5-10 minutes into playing a game. It shows up on all games but it comes through more on light colored backgrounds. Does anybody have any clue how to fix this or what it is exactly? Below is a link to the other post I came across discussing my same issue. 

 

 

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Hey Zerosquare. Thanks for the reply. Yes, here is a link to the video I posted on youtube. It looks worse in person. It's tough to concentrate on actually enjoying the game (I'm sure my OCD is helping much either). I haven't opened it up yet to see, but I just have this gut feeling that it has and ACD chip, which may be causing the issue as mentioned in the other posting I've seen. I'm tempted to try what the user, Stephen Moss, suggested which was to either remove the R110 which would remove power from the ACD chip (U16) or remove the ADC chip (U16) completely...

 

 

 

 

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I don't see how it could be related to the ADC chip: it has no relationship to the display, and it does nothing unless the game explicitly uses it.

 

Early Jaguars had a few manual modifications added to the PCB, including one involving the clock circuit ; that's the blue wire on the picture below:

IMG_20140429_214413.jpg

 

I don't remember seeing anywhere which problem it was supposed to fix, but maybe it was this one, and for some reason your Jaguar didn't get modified?

 

 

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Zerosquare is correct in that it is unlikely any problem with the ADC would cause display issues, but not impossible if, say they were causing dips in the power rail.

In the post referenced the original poster indicated the issues was only with units that had ADC's and theoretically only difference between units should be the inclusion of the ADC's a logical first step to me would be to disable/remove the ADC's to see if they were the source of the problem, which is why I suggested it otherwise I would not have looked at the ADC's first.

 

It is not clear from the original post if the issue is occurring with all carts in which case it is defiantly the Jag or just Atari Karts? 

 

It could be a bad address or data line, I don't know what data error checking the Jag does but it could be that upon an error the data value is set to 0 and that results in black pixels. The fact that it occurs 5-10 minutes into play may suggest a bad solder joint as thermal expansion may then cause an open circuit.

If you have something small and non conductive such as a lolly-pop stick you could try pressing down on the soldered part of the pins of TOM (U13), U7, the cartridge connector, the 68000 (U29) and the RAM (U23, 24, 33 & 34) to see it if the problem clears at any point.

If the problem did clear up when pressing on a particular sport not only would that appear to confirm a bad solder joint problem but also narrow down which pins need re-soldering.  

 

 

Edited by Stephen Moss
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OK. That makes sense.I appreciate the responses on this.

 

Thanks for the response on this post Stephen. It happens on all games. However, it’s not as noticeable with darker backgrounds. And yes, after about 5 to 10 minutes it starts to become more visible. I’m gonna go ahead and look into what you suggested and report back.

 

Thank you for the suggestions

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