Question for Vector Oscilloscope Users -- How to Invert the Z signal?

fuji8bit

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Hi Everyone,

I recently purchased an analog Oscilloscope (Tektronix 2235) that has XY mode and a Z channel so I can troubleshoot my vectors more efficiently.

I hooked up a Vectrex I'm working on, and everything works fine except the Z signal is inverted. The Oscilloscope intensity is the inverse of voltage (where voltage is 0-5V peak to peak). The result is that I'm seeing the redraw lines and not the vectors.

What I need to do is invert the signal before it gets to the O-scope so I can see the vectors correctly. To my knowledge, there is not an "invert" button for the Z channel (unless one of you knows of one?).

Is there a device, ready made for this? Or should I build my own circuit?

links or schematics are appreciated!

Cheers,
Steve
 
I've never used the Z signal and it works fine. Try it without the Z signal connected.
 
I've never used the Z signal and it works fine. Try it without the Z signal connected.
Thanks -- do you end up seeing all the vectors (including the redraw ones?). I understand that is better than what I have now, just curious :)
 
Thanks -- do you end up seeing all the vectors (including the redraw ones?). I understand that is better than what I have now, just curious :)
This is an example of what I saw. You can look up my Asteroids troubleshooting thread for more scope pictures.

1678890836831.png
 
thank you again, that is what I'm going for :).

I also looked over the schematics for the Scopetrex, and it appears they have an inverter circuit for the Z-input (with a polarity toggle switch). I will breadboard that out (only one IC and some resistors) and post pics when I'm done. Credit for the schematic to https://github.com/schlae
 

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Yes, there is a device, as you've seen. But you don't need it.

The goal shouldn't be to get a 'perfect' image on your scope. Seeing all of the drawing lines just gives you more info, which is better for troubleshooting.

You can look at the Z signal separately if you think there's a problem there. But Z circuits and problems are usually pretty easy to identify and fix (as they're usually either working or not).
 
Yes, there is a device, as you've seen. But you don't need it.

The goal shouldn't be to get a 'perfect' image on your scope. Seeing all of the drawing lines just gives you more info, which is better for troubleshooting.

You can look at the Z signal separately if you think there's a problem there. But Z circuits and problems are usually pretty easy to identify and fix (as they're usually either working or not).

I see what you're saying -- but I did notice something about the vectrex.

The way it draws objects (in Minestorm, at least) is that it always returns the beam to the center before drawing the next object, giving the O-scope display a "starburst " effect, and a really bright center dot in the middle of the screen (which I try to avoid). Blanking those lines would eliminate the "noise" and the center dot (and closely emulating the vectrex monitor display).

If I'm correct, Asteroids (at least on the screen @ArcadeTechGW shows above), it appears as though the display *is* drawing the retrace lines, but the beam is not returning to the center of the screen between letters :). It appears the Atari programming is a little less messy. I'll post some pictures next week when I get home.
 
I see what you're saying -- but I did notice something about the vectrex.

The way it draws objects (in Minestorm, at least) is that it always returns the beam to the center before drawing the next object, giving the O-scope display a "starburst " effect, and a really bright center dot in the middle of the screen (which I try to avoid). Blanking those lines would eliminate the "noise" and the center dot (and closely emulating the vectrex monitor display).

If I'm correct, Asteroids (at least on the screen @ArcadeTechGW shows above), it appears as though the display *is* drawing the retrace lines, but the beam is not returning to the center of the screen between letters :). It appears the Atari programming is a little less messy. I'll post some pictures next week when I get home.


Fair enough, if you're working on Vectrex. I wasn't aware that it centers after every vector. Atari games don't center as much (and some games more than others. Tempest does it more than Asteroids.) But not to the point of making it unreadable.

Generally with scopes though, you just want to see if there's an image there or not, and if it's roughly correct. For fine picture details, you need to view things on a monitor.
 
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