Angled lines tracing across the vector screen to objects

[Justin Z]

Hi guys,

You may have seen my thread in the main forum about an Asteroids Deluxe cocktail I am looking at.  The owner claims it needs a cap kit because of the problem in the attached picture which I tried my best to simulate using a paint program.

There are angled lines following all the objects around the screen.  It is really quite strange.  In addition, there are bright white dots in the center of all the objects -- the dots are FAR brighter than anything else, and it's an effect only a vector monitor can show properly, so I just drew them as white dots on this mock screenshot.  Take a look at it and see what you think.  Note also there is also pretty bad blurring of the text both at the top and bottom of the screen -- this is intentional as I noticed it right away.

If I can cap this I am going to attempt it.  A more extensive repair though, and I'd shy away from it due to my utter lack of experience.

Thanks for your help.

[grantspain]

looks to be a game board fault,don't look like a monitor problem to me

[Justin Z]

Interesting.  I really don't have the slightest understanding how vectors work so tell me -- why do you think it's a problem with the gameboard?  What is it "telling" the vector monitor wrong that would be causing the display to look this way?

[D_Zoot]

For some reason your picture is dark on my monitor, so it's hard to see what it looks like, but from your description all of the vectors are being drawn properly but there are lines connecting all of the vectors together ??

If so, start by adjusting the brightness and contrast controls down on the monitor.  If these are set too high you will see these lines.

If that's not the case, then you probably have what's called the "Z Channel" problem.  The Z signal controls intensity or brightness.  This sort of problem can be anything from a bad connection at either the board or monitor, or a monitor or gameboard problem. 

But in the bulk of the cases I've seen, it's usually just an improperly adjusted monitor, actual Z channel faults aren't common.


D
 

[Justin Z]

Thanks D_Zoot.

Chad mentioned a similar phenomenon to what you were talking about in my original thread about the cab in the main forum.

So when I went to look at it I had that in mind.

The thing is, I drew the mock screenshot dark because the intensity of everything is pretty low, EXCEPT for the bright white dots in the middle of all the objects.  So I don't think it's an adjustment problem.

It'd be great if it were just a bad connection . . .  But the question then becomes, is it worth the risk to find out?

Thanks for the info.  Also, I brightened up the screenshot to give you a better idea, here it is.

Justin

Edited to add:  Now that you said "connected together," I think you are right.  I think there are actually lines connecting the objects together too, not just lines to the edge of the screen.  This is why I should've brought a camera. 

[D_Zoot]

It sounds like the picture is dim due to a monitor problem, so somebody cranked up the brightness to get a picture out of it,  which brings out the connecting vector lines.

Could be a few things from bad caps, low heater voltage right to a weak tube.  Generally those tubes were pretty robust, weak tubes aren't very common (they developed severe screen burn long before the electron gun got weak, if screen burn is minimal I doubt it's got enough hours/days/years on it to wear out the gun), so that would be last on the list of possibilities.   

Rebuilding the chassis and freshing up the connections could very well bring it back to life! 

If it's worth the risk is your call dude...      


D
     

[qrz]

i'm gonna give this an "educated guess" as a blanking problem in z drive. the drive signal should be blanked when moving from image to image .   this is similar to visible "retrace" on  crt type tv's/monitors.....
look for an open or leaky xistor ..  a schematic would be helpful !!

qrz

[ChadTower]

The thing is, I drew the mock screenshot dark because the intensity of everything is pretty low, EXCEPT for the bright white dots in the middle of all the objects.  So I don't think it's an adjustment problem.

Yes, it is, and I explained why it would be an adjustment issue in the other thread.  D-Zoot has mentioned a second possibility, that of a Z voltage problem, which is also a good suggestion.