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Thread: CYGN-A

  1. #21
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    Click image for larger version. 

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    The freq pots are not grounded. Oh and my drawing has a error. I'm pretty sure the 1meg pots were dual reverse audio taper.

    The spiral select switch was the image source for the spiral card. Originally on the Mark IV the spiral source was a fixed quadrature osc on the spiral card with the Mark VI and maybe Laserock the existing switch was retasked as a spiral source select. Originally three positions and eventually five. CYGN-A, CYGN-B, KQO, and two others I can't quite recall were the new sources.
    "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

  2. #22
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    1. CYGN-A
    2. CYGN-B
    3. KQO
    4. DANUBE 8's
    5. DANUBE 0's
    "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. #23
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    Mar 2010
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    And thus, a slice of history is revealed in a log book entry. The photo shows this circuit built using a KIA324P quad op amp. The output is a beautifully tunable quadrature. But the output amplitude is only slightly over +-1V. Is this correct? I notice the 10K in the summing amps suggests some gain there.

    As the SPGN schem receives my closer attention, I realize that I don't have a clear idea of what this circuit actually does. I see the inputs for an external cycloid. It is like a VCA in which a shaped ramp modulates gain? Or is the ramp for the "sweep"? Is the sweep a varying offset in one axis? What is PDM out? Spiral in rate control? How was the reset used? Your comments, as always, and as your time permits, are very much appreciated.
    Attached Thumbnails Attached Thumbnails CYGN-A_oscillator.jpg  


  4. #24
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    The spiral card had 3, 0 to 10 volt inputs from the 351 data, and two digital inputs. Out rate, in rate and sweep were the analog signals, spiral reset and diamond spirals were the digital inputs. So you could control how fast the ramp generator ramped up and down, reset the ramp, and the sweep was summed to the image input. The ramp generator produced a ramp and an inverted ramp. Two pairs of 2QMMs modulated the input/sweep as spirals and inverted spirals. Analog switches could apply the other ramp to one input of the multiplier pairs for diamond spirals. I've never looked at the ramp gain. I assumed it's 0-10 V, but the key is the resistance before the 2QMMs. The PDM output was a square wave at the spiral frequency that was used as an offset on one axis of the fixed cycloids. Originally used in "Summer Madness" in Laserium I.
    "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

  5. #25
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    An error causing the low amplitude of the CYGN-A oscillator was found. Photo shows the three oscillators.

    Other photo shows the collection of the less common semiconductors which should be able to become the SPGN, except for the Burr Brown, with which this build will have to do without. If I may ask, what is the part of the circuit that contains the dual transistors doing?
    Attached Thumbnails Attached Thumbnails CYGN-A_3oscillators.jpg  

    SPGN_rare_chips.jpg  


  6. #26
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    The dual transistor in the spiral ramp circuit is similar to the 2QMM circuit. I'm guessing, but I believe it was to get a log frequency response from the 0-10 volt up down ramp control voltages. You see it in audio synthesizer circuits where they're after one octave per volt VCOs.
    Last edited by laserist; 02-23-2021 at 08:06.
    "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. #27
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    I'll send the BurrBrown chip with my next shipment of Laserium artifacts. It just occured to me that it might be a cool effect if you used the ramp shaper on just one axis. It might be similar to the KQO symmetry effect.
    "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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