I built a scopetrex! Vectrex games on my old oscilloscope
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- Опубліковано 7 вер 2024
- While wandering the Internet one day, I came upon the plans for the scopetrex, so I went ahead and built one! The vectrex was a vector-based game console from the 1980s. Whereas most home video game systems of the time used raster display, usually on your television, the vectrex came with its own internal screen and drew monochrome vector graphics. Vector graphics are drawn by continuous positioning of the electron beam to draw out simple shapes. You get pure figures that lack the pixelation often seen in early raster games. Anyhow, I followed the plans, I built the scopetrex, and I tried to get the display properly aligned, with some limited success, though it's still far from perfect. In this video, I play a few popular vectrex titles including "Scramble", "Mine Storm", "Star Trek", and "Pole Position". For more electronics projects, see www.smbaker.com/
I love the idea of making a TV into a vector display, as a kid I saw an arcade version of Space Wars on a giant CRT it was an amazing experience back in the 70’s. I would love to create this with a converted TV and a ScopeTrex. Thanks for the video
Unfortunately TVs don't make very good vector displays - the tube is not a problem, but the deflection coils and drive circuits are designed to scan much faster in one direction (line) than the other (field) - in the case of a US NTSC TV, the field rate is about 60Hz and the line is almost 16kHz, so you have ~250x the bandwidth in one axis over the other. Another issue is that a TV typically uses an overwinding on the line transformer to generate the high voltage for the tube, so in the absence of any repetitive line drive signal you need to do some major rework on the line circuits.
Things I tried:
* Clean off all the solder flux - maybe some difference in adjustment, but no improvement
* Replace Integrator caps with WIMA MKP2 Poly Caps - moderate improvement
* Replace Sample-and-hold caps with WIMA FKP2 Poly Caps - significant improvement, especially in the Y axis. Weird "blank spot" in the "Integrator Test" text went away.
* Replace DAC0808 with one from Jameco; Also tired ebay MCP1408 - no change
* Replace overclocked 6809 with a 2MHz 68B09E and replaced crystal with oscillator - no change
The impact of switching to the poly caps was significant. It's not perfect now, but it's a lot better than it was. I am considering changing the remaining 47pF caps for poly caps as well, to see if that has an impact.
Wow, this is so very impressive!!!
All of your videos are a pure distillation of awesomeness.
Looks like you may have used ceramic caps in the integrators. Replacing them with poly caps may help. The linearity of these caps is critical.
hmm, I don't have any appropriate poly on hand. What would you recommend? Wima MKS or MKP, for example ?
@@smbakeryt Anything from a reputable manufacturer/supplier should be fine. Would be interesting to compare polypropylene, polystyrene, and NP0 ceramic (much better than the common X5R ceramic).
I also think it's the caps in the integrator circuit, I had a similar problem when I recapped my vectrex, then I replaced the caps in the integrator circuit for the poly caps, and all was good again. I used these from mouser. FKP2C014701D00HSSD and FKP2C021001G00HSSD.
@@patzik1910 Thanks to you and @oPossum5150 both. I went ahead a few nights ago and ordered some Wima caps. The very same FKP2 4700pF for the sample-and-hold. I went with MKP2 0.01uF for the integrator (hope that doesn't turn out to be a mistake; the WIMA application seemed like either would do)
@@smbakeryt Were you successfull with the change of capacitors? Is the geometry of display OK now? Thanks.
Fwiw - I had that same scope. Gave it to my dad a few years ago and as I recall he had found some common problem with it. I will call him tomorrow and ask him about it.
Could be a few things such as the Scope itself since it is meant for displaying waveforms and not video, could be the ceramic caps or the slew rate of the opamps.
I'm building one of these too! Neat design. Question for you: Where on earth did you find the 3 ferrite beads the board needs? I'm having trouble sourcing some.
Hi! I have ordered ferrites on the Aliexpress page. Have you already built the scopetrex PCB? What are your results, experiences? I have not finished it yet and I am curious.
@@tomaskozeluh2211 I am going to look at Aliexpress to order (thank you!) and will start building soon. I will post the build on my channel as well. I want to use a Mac Plus 9" monitor (re-wired for vector) and build a Vectrex clone.
Congratulations!
On your display alignment challenge: the problem is that your oscilloscope display has a correct and linear response to deflection voltages, where-as the Vectrex display implementation did not (was non-linear.) The Vectrex logic board deflection outputs were non-linear, to match the reactivity of the Vectrex display, and (presumably) this newer implementation mimics this. I've seen (somewhere) a simple circuit which is a ladder of some resistors and a capacitor which can be put in the output path(s) to make a linear tube act more like the Vectrex display. You'd find this employed, for example, in implementations where a Vectrex drives and arcade vector monitor. Try some judicious web searches...
I like it alot. Your alignment will be related to your PSU voltages. the Minus voltages will drive the "Dot" to the negative quadrants. "+" up right is pos X Pos Y, low right is pos X neg Y, ect. if one of your voltage rails is off then it will be distorted. I had to work on this type of deflection system while in the NAVY for the operator consoles. test was hard to get right but with practice it was able to be done..... You PSU first then the voltages from the deflection D/A converters. May also be an issue with your scope!
Interesting the 3D printed box for scopetrex. Can you share the STL file somewhere ?
DARN this is cool, another LIKE :-)
Outstanding!!!
I would probably build me a laser projection screen out of two old hdd arm coils and magnets. The screen size you can achieve there is pretty nice and it’s small and lightweight. The only tricky part is the 2-axis mirror hinge which have to move precisely and quick enough to allow for the laser scanning.
Sadly absolutely not fast enough
Yesssss
This is amazing! To help with the remaining alignment issues have you tried clipping calibrated CRO probes directly onto the PCB?
Nice video, thank you :)
Has the scope probe compensation been corrected? The input to the scope is designed for a standard 1x or 10x probe. When you direct feed coax signals there is ringing due to impedance mismatch.
Hello "smbakeryt". Please, have you improved the geometry of display, is it OK now? What exactly was wrong? Thanks
Did you know that some unsold Vectrex units actually had their monitors recycled to be oscilloscopes?
are the DACs made up of discrete resistors. Most dacs of the time were built up using R & 2R ladders or resistors in a 1,2,4,8, chain to get the proper steps between lines, if so, the display seems to show you have one of the dac resistors to far off value on the vertical axis or the horz also. hense the different gap / bar above the lettering and the misalignment of lines in the calibration. if your dacs are made up this way recheck all the dac resistors values very carefully . is there a schematic avaliable.
Great video thank you! Is there an indication a scope has z axis blanking? I’m assuming there is a switch
Really enjoyed can I ask do you know how I can use a mic thankyou
DE-9 connectors. DB is wider.
Now you just need to make the PDP-1 to go with it...
#Spacewar
The oscilloscope : the original arcade table tennis system.
Does this make it possible to stream the Vectrex on twitch?
I don't know why I feel compelled to say this (because it is pedantic and stupid), but *technically* those are DE-9 jacks and not DB-9. The letter after "D" is the size of the jack, so "B" would be huge like an old parallel port, and "E" is the size of an old serial (and also VGA) ports.
could just call them d-n jacks in most cases, the number of pins usually shows the size, (VGA / game port being the obvious exception)
It can be useful knowledge if you use D-sub connectors in projects. a while back, an engineer ordered a few thousand DA15 connectors instead of DE15s for a production-level repair project, and we got stuck with a large pile of unusable connectors. A DA15 is like the connector used for old Mac RGB monitors. the DE15 is used for VGA.
You're right, and I know you're right, but force of habit leaves me calling them "DB-9s".
Well, time to look for old oscilloscopes on eBay.
Just make sure you get one that's "old, but not too old". Several of the really old vacuum tube scopes, for example, look nice but might not have the Z-axis modulation. I do have a nice Eico, for example, that I'm thinking of figuring out how to add the Z-Axis to it.
the fact that you didn't play the bad apple demo is mildly disappointing
Did someone make a vector version of it?
I don't have it! Is it in the public domain, or must it be purchased? I can look into adding it to a follow-up video, if there is one.
@@smbakeryt it's a homebrew, I'd link it but my comments keep getting deleted
@@pacman10182 weird, I can't imagine why your comments are being deleted. You can always email me at smbaker@smbaker.com
@@smbakeryt I'll do just that