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Thread: PT-30K scanner troubles

  1. #11
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    The main reason I went usbstreamer and adat was because of digisynth. So I am going to try and make computer to usbstreamer to the blackface to the projector work.

    At this point though I don't know what is causing my issues. I friend of mine is going to bring a sig gen for testing this weekend so we can work out where I am having my problem.

  2. #12
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    If I ever get home from work tonight Iíll send you the link for the ILDA test pattern in wave form. I typically use foobar2000 for playing wave shows and N-Track for recording.

    The USBStreamer is an awesome little device, I can even playback and record lasershows with an iPhone or iPad.

  3. #13
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    Documentation is a little spotty for it though. In the usbstreamer menu it says 8channel 24 bit. But software/Windows says it's outputting 16 bit. I am hoping that is just the max bitrate that is listed in the menu, and not the reason I am having problems. Blackface being 16 bit and all.

  4. #14
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    Quote Originally Posted by Theoneinformant View Post
    Documentation is a little spotty for it though. In the usbstreamer menu it says 8channel 24 bit. But software/Windows says it's outputting 16 bit. I am hoping that is just the max bitrate that is listed in the menu, and not the reason I am having problems. Blackface being 16 bit and all.

    Do you have access to an audio signal generator with sine and square wave outputs? Not a sound card or adat if possible, but an actual stand alone signal generator.
    You need a dc coupled, variable amplitude, symmetrical, Thirty Hertz square wave to start on scanner diagnostics the professional way.
    An Oscilloscope would not hurt either, but once you have a square wave of good quality I can walk you thru some quick checks with the laser.
    ~
    My method is the old way, also the factory way, and it works when all else fails. Beware of imitations, because I have the Cambridge Technology book on how to do this from scratch if your a laser show person. They used to give a presentation on hard core scanner amp factory tuning methods at ILDA Conferences. The guy giving the course was Mike Thanos, who co-designed many of these scanner amps. He showed us old guys a few useful things when we were young. You then need a quad square, a Laser Media test pattern, and the ILDA pattern next.
    ~
    Once you touched the potentiometers, there is a good chance you need to tune from start.

    Steve
    Last edited by mixedgas; 03-27-2018 at 07:44.
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  5. #15
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    Yes, my buddy is bringing by a sig gen from work, and I have a fluke 199c to use. Not a full o scope but I can read waveforms. And as long as I can get those waveforms from DZ I should have everything I need. Your help would be greatly appreciated

  6. #16
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    First test. This assumes that you have not messed with the image size or servo gain potentiometers that much.
    0. Observe laser safety procedures.
    1. Pick an axis. Usually I start with the smaller "X" mirror.
    2. Ground one side of the scan amp differential input to ILDA pin 25. Connect the ground side of the signal generator to ILDA pin 25 (ground), make sure pin 25 is connected to galvo psu ground(s) Ground both inputs of the other amplifier. This should give you two dots along the zero line on the screen as you turn up the amplitude when things are working.
    3. Set a signal generator to ~ 30 Hz square wave and set its amplitude to zero
    4. Connect the hot lead to the output of the signal generator.
    5. Power up the projector. Somehow tie one of the lasers on, observe quiet non-moving dot that is not a line.
    6. Slowly turn the deflection to about 10 degrees optical, mark the location of the dots on the wall.
    7. Observe two clean dots, slightly flickering, staying in position, little or no ringing. Nearly zero overshoot should be observed. Should be left and right of zero point evenly.
    8. Power down.
    9. Flip the grounded lead and the hot lead, power back up. Dots should be symmetrical, in nearly the same position and any distortions flipped. If not, problem with signal symmetry in amplifier or bad offset in signal generator output.
    10. Ground both leads, should go to one dot and be centered. Then switch back to
    11 Switch to sine wave. you should see a smooth line with a slight brightness gradient in the center. Should be No slope, no position drift, and should be centered on zero point. Slowly increase frequency, note any resonances. If you find a resonance where the signal blooms in width, quickly tune past it. Note frequency where line width starts to shrink, note this frequency.
    12 slowly turn up frequency and note where sine wave line becomes 75% of original length.
    13..Do the same starting at 15 degrees optical. Note frequencies as before.
    14. Do the same at 20 degrees optical. Note the frequencies should be decreasing as angle increases.
    ~
    Do the same for the other axis.
    ~
    If both axis look about right in above test, connect x and y input together to 30 Hz sine wave. Line should be diagonal, switch to square wave, you should see dots rotated 45 degrees relative to marked dots from both axis.
    ~
    More coming. I need to take and clean up some scope shots. Those are low cost clones with a weak output stage, and I have no idea if they brought out test point 2, which is the raw position sensor output. From the manual it looks like they did not.
    ~
    Find a roughly 0.1 Ohm resistor near the galvo cable. This is the source of the other feedback signal on the board, it is a current sensing resistor. One end of the resistor should tie to analog ground. The other end should go to the low end of the galvo coil. It really helps to monitor both test points with a dual trace scope. The current waveform when driven with 30 Hz will NOT mirror in the input signal, far from it.
    ~
    I'll finish the post later.. I need to shoot some scope pictures.
    ~
    Steve
    Last edited by mixedgas; 03-27-2018 at 16:07.
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  7. #17
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    I had a similar issue from a broken crimp on one of those breakout boards. How like Lovell drivers. They are pretty good. Just picked done up. Solder the diode. Those crimps do come loose and if they do on the diode good night Irene. Drivers great crimps not so much.

  8. #18
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    After I figured out that I didn't have the grounds ries together they work great. Breakout board tests good, that was the first thing I checked. All crimp connections are tinned then crimped, very solid connection. I also use a hydraulic crimper, so it really does a good job.

  9. #19
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    Damn, thank you Steve. I will definitely get on this as soon as I get home for the weekend, should be Friday afternoon. I will report my findings

  10. #20
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    As someone who uses Digisynth and the USBStreamer frequently, that should be rather plug and play. I've never seen such an issue.

    However, if playing back from an audio software automatically mixing a track or two of multichannel into the wrong channels, you can get some oddities there.

    If you haven't done so already, eliminate as many variables as possible, confirm you have good signals, run things inbound from a database into preview window or onto another device, use a known good confirmed signal source, etc.

    Good luck!
    -chuck

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