Asteroids "fold" ??

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Hi;
I have an Asteroids that I just picked up and the display has this weird "fold" in 3 areas of the display. One on the left, center and right side.

During game play, when the player ship crossed one of these "folds", it appears that it actually folds back on itself as it crosses over.

The voltages are correct and during test, no errors are present but obviously there is an issue somewhere on the PCB.

I attached pics and a link to a short video.

If anyone has come across this situation before, I'd appreciate some guidance.

Thanks in advance.
Jeff

VIDEO: http://youtu.be/-p8EvOgvSuY
 

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I just realized that I have this same problem on my Lunar Lander, just that it happens on only one area of the display, not three like the Asteroids.
I always thought it was a damaged area of the CRT that caused the lander to "fold" while crossing that point but now I am thinking that it is actually a board issue (just like the Asteroids)!
That's both good and bad as I don't have to replace the CRT in my LL to correct the issue (good) but I still have to find the cause of the "fold" (bad).
Jeff
 
Any pointers would be greatly appreciated!!!!
I'll be able to kill two birds with one stone - so to say...
PETA: I would never harm a bird!
 
OK, I went and adjusted the display, expanding it beyond the visable portion and also shrank it down to the center of the display and the 3 "bad" areas remained in realitive positions as before, they followed the size of the display so I am now leaning towards a board issue.

To explain the situation in better detail, picture the display being devided into a vertical grid of 4 rectangles ( 4 tall rectangles side to side ). So the high score table is devided half and half across grid box 2 and 3 and the player 1 score resides in the upper area of grid box 1 and player 2 score resides in the upper area of grid box 4.

What is actuall happening is grid box 2 is slightly over on grid box 1 and grid box 3 is slightly over grid box 4, leaving a small "gap" in the center of the display where no vectors are being drawn.....as grid boxes 2 and 3 have seperated. Even though the grids are overlapping, they are still connected, hence the little "reverse" when an object passes over that area.

I will pull the PCB and go over the caps (thanks for the suggestion) and see what I can find.

Very strange .......

Jeff
 
I had the same thing on an Asteroids board and it was either the TL082 at A12 (Y) or C12 (X) or the expensive digital-to-analog converters AD561J at B11 (Y) or C11 (X) all in the analog output section of the game PCB.

Bad position counters LS191 at F9 H9 J9 (Y) and C9 D9 E9 (X) would produce a more 'digital' error (e.g. a diagonal line would look like a stairstep).

Looking at your video I'm afraid it's the DACs but you could try the TL082s first since they're way cheaper. But it's probably the DAC.
 
Thank you for the insight / suggestion, much appreciated especially since this is outside my level of expertise.
I will check this out and post my results.
Jeff
 
BTW, since the anomaly affects the lines going from the top to the bottom, do you think it's the "y" channel that is defective?
Thanks
Jeff
 
BTW, since the anomaly affects the lines going from the top to the bottom, do you think it's the "y" channel that is defective?
Thanks
Jeff

Actually what's missing (or doubled) is when the beam tries to move to a certain position to the left or right, so it's the X channel.
 
Thanks for the clarification, I will check the "X" channel first.
I am going with the TL082 (cheap!) but of course, I do not have them in stock so I will have to order them.......
I will update the thread once I have some results.
Thanks again for the help.
Jeff
 
Did you ever figure this out? I have an asteroids deluxe that's folded in HALF top to bottom, I believe it's probably the DAC. I'm going to try and swap the two, and see if that makes the screen fold like a book.
 
I messed with mine today. Basically, the entire top half of the screen was folded over the bottom half of the screen. Still completely playable. If you read the schematics, the way it works is the DAC's take the information and it's eventually turned into a number, the higher the number the higher up the screen the image is, etc.

If you have a monitor issue, it doesn't do this. The monitor, when it loses the top half, compresses everything that should be in the top half into a single line in the middle of the screen; it doesnt' fold it back down over the other image.

So I looked at the schematics, and there's a 4016 chip just after the DAC's on the X and the Y. The signals looked a little weird on the Y circuit, so I replaced the Y circuit's 4016 with an upgraded 4066 (heftier version of the 4016) and it fixed the board.

BTW, Mine also has some minor fold issues like yours does, but it's so minor I'm leaving them. It's literally like a pixel wide or two or three pixels wide on mine, in the three seperate spots vertically, but it's not enough that i'm concerned. I've had other Asteroids machines with the same exact thing, too, and it doesn't bother me.
 
I had the same thing on an Asteroids board and it was either the TL082 at A12 (Y) or C12 (X) or the expensive digital-to-analog converters AD561J at B11 (Y) or C11 (X) all in the analog output section of the game PCB.

Bad position counters LS191 at F9 H9 J9 (Y) and C9 D9 E9 (X) would produce a more 'digital' error (e.g. a diagonal line would look like a stairstep).

Looking at your video I'm afraid it's the DACs but you could try the TL082s first since they're way cheaper. But it's probably the DAC.

I also had a similar issue and it was the AD561J that was bad as well.
 
I have plans to attempt the repair of my PCB this weekend, as well as several other projects that need my attention, we shall see........

Thanks for all the tips and suggestions.

Jeff
 
Just adding my two cents here, I've seen this issue a few times before and it's always been the DAC's.

If in doubt, you can socket them, then swap them and see for certain that the problem changes axis.
 
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