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Thread: CYGN-A

  1. #111
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    Interesting. The latest show I saw was Crystal Odyssey. If my understanding is correct, the Beatles came after that. I haven't heard of the clipper card. I don't see it referenced in the L.II system diagram hybrid card cage, nor in the L.6c system block diagram, nor in Ron's 6b alignment procedures doc.

  2. #112
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    Sorry, the clipper card wasn't added in 82 it was added in 81. It was modified to add AO Driver in 82. I'm guessing the Clipper board and controls were added as part of the Crystal Odyssey Mods. The Clipper did what it's name implied. It gave the Laserist control over where the positive and negative ends of the X & Y signals (from the master gain control of the CYGN-A) were clipped. The two clipper circuits used one each of the AD811 and AD821 dual transistors so a it would take a bit of a redesign today. FWIW I never liked the clipper effect on the G-124 open loop scanners, and I never saw anything cool enough to make me really want to use it. I'll try to make it by UPS this weekend and send the packages sitting on my steps.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

  3. #113
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    Awesome! Looking forward to that. Yeah, I remember the opening number of Crystal Odyssey had something that was like Danube circles but if I remember right it was more like rounded rectangles. Maybe that was evidence of the clipper.

  4. #114
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    More time spent hunting microscopic flecks of conductivity than I would prefer, but the spiral and effects board is ready to be wired to the panel. Then I'll finally get to the exciting part: setting up a bunch of Single-ended-to-Differential Signal Converters and controlling a projector without the use of a DAC. I can't wait to see how the colormod looks.
    Attached Thumbnails Attached Thumbnails effects_module.jpg  

    ILDA_port.jpg  


  5. #115
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    Wondering if there's a story about the chopper signal. Guessing a variable width square wave from a 555, though maybe it listened to the spiral generator at times for retrace blanking.

  6. #116
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    The original chopper was a General Scanning G300 series scanner with a slotted can shutter. That produced a soft edge effect. With the Beatles show it was replaced with an AOM. Hard edges, but much faster. There were 4 toggle switches to set the chopper mode. One for PDM. Two to select between 0, 1 & "multiplex drive", and one as an enable. Later a PCAOM or two replaced the AOM. As Laser Images got older and smaller improvements happened on an increasingly intermittent time line.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

  7. #117
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    The circuit, as proposed by Brian, has produced results. The parameter varied in the photos is the gain of the sinusoid input to the colormod. The R Y and G colormod channels are driving the R G and B inputs to the laser. Next up will be the summing amps needed for the Y color channel. Also needed functions include channel intensity attenuation and input for a blanking signal.

    I may have found a use for the triangle wave CYGN-B oscillator: good effect when followed by the diamond spirals modifier, and bringing up the sinusoid on the same oscillator is a lick.
    Attached Thumbnails Attached Thumbnails colormod_emu_circuit.jpg  


  8. #118
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    If you hook up a pot that allows you to offset the colormod signal you'll have something akin to the beam torquer that is right in the center of the console. To recreate the four scanner Laserium look you'd need four comparitor circuits with different fixed offsets for each scanner "color". And four RGB projectors obviously.
    Last edited by laserist; 05-16-2021 at 10:53.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

  9. #119
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    Quote Originally Posted by laserist View Post
    If you hook up a pot that allows you to offset the colormod signal you'll have something akin to the beam torquer that is right in the center of the console. To recreate the four scanner Laserium look you'd need four comparitor circuits with different fixed offsets for each scanner "color". And four RGB projectors obviously.
    Regarding the four scanner Laserium look w. 4 comparator per channel, fixed offsets, that's an excellent point of design. I want to do exactly that eventually.

    Regarding the signal offset pot, I am doing that immediately. I'm building another of the CYGN-A and B bipolar ramp generators with offset.

    Somewhere in these threads it was revealed what colormod I was, and what the row of buttons above the beam torquer did. Trying to find that comment...
    Attached Thumbnails Attached Thumbnails colormod_emu_circuit_RYGB.jpg  


  10. #120
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    Colormod I was just a 555 timer based Voltage to Frequency Oscillator (VFO) that drove a counter that generated a course "sine wave" output. As in the CYGN-B the VFO allowed for frequency modulation of the Color Mod I signal. The first three buttons left to right summed the CYGN-A outputs to the Color Mod II outputs. Two of the next three enabled the Color Mod II signal to AM or FM the Color Mod I signal. The last button simply enabled the Color Mod II signal to sum to the Color Mod scan amp. The Beam Torquer, CM1, & CM2 had different looks - but all were produced by the same scanner.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

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