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Thread: DT-40 Pot Assignments

  1. #1
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    Default DT-40 Pot Assignments

    It seems that I inadvertantly deleted the pic that I posted of the DT-40 pot assignments in this thread: http://www.photonlexicon.com/forums/...ght=dt-40+pots

    Does anyone have a copy or can tell me what the pot assignments were? I was working on a show and my X scanner went nuts. Now that I have that problem resolved it needs some serious tuning.

    Thanks

  2. #2
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    Yaddatrance does a great write up here:

    http://www.photonlexicon.com/forums/...ead.php?t=2266

    there is a PDF attached to the post about 3/4 the way down. There are some great tips there and things you can do to bypass some of the nonsense that was incorporated into the DT-40s because 'the other guys were doing it'

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    Thanks mliptack, that thread is regarding the DT-40pro's. I'm looking for the pot assignments for the original DT-40's. Unfortunatly, quite a big difference between the amps.

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    Oh shoot.... sorry, I just glanced over the post. My mistake.

    Well with my stupidity aside... sorry I can't help you out then

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    Well with my stupidity aside... sorry I can't help you out then
    No problem, thanks for trying though!

    Ok, so I thought I had the issue fixed, now it looks like I don't. Check out this video. Whatcha think? I've isolated the problem to the X amp, not the galvo. Visual inspection yields no clues. I pulled out the O'scope and check around a bit. What I've found, is that when it occurs, the signal from the amp to the galvos become cliped on both the positive and negative rails. Just still haven't figure out why.

    Video is 17meg, not sure how to cut it down.
    https://home.comcast.net/~djzurcher/dt40.MPG

  6. #6
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    Quote Originally Posted by DZ View Post
    What I've found, is that when it occurs, the signal from the amp to the galvos become cliped on both the positive and negative rails. Just still haven't figure out why.
    Have you tried heating and cooling sections of the board to narrow it down to one area? Perhaps its a feedback problem?
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  7. #7
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    Have you tried heating and cooling sections of the board to narrow it down to one area? Perhaps its a feedback problem?
    I haven't tried that yet. It could indeed be a heat problem, makes me wonder if the LM3886 IC is bonded well enough to the heat sink (Frame). The problem only seems to start with that particular abstract, which is rather complex. It seems to do rather well with everything else and its never had a problem with that abstract before.

    I still could use the pot assignments if anyone has them.

    Thanks

  8. #8
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    Hmm,

    If its a problem with a abstract, perhaps it has something to do with the power limiter?
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  9. #9
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    If its a problem with a abstract, perhaps it has something to do with the power limiter?
    I'm not sure, the Y axis is completely unaffected. I've displayed that abstract for a few minutes and the Y never collapsed. Oh well, I'll have to play around with it more tomorrow. I'm starting to think that it is heat related. Perhaps, if there is any thermal compound between the audio amp IC and the heat sink, maybe it has broken down and is now acting more like an insulator. If thats the case, eventually it will happen on the Y axis. Anyone else experience strange issues like this with the original DT-40's? Aside from this small problem, they've been flawless for me. Must have something to do with that damn smiley in my avatar, how did that get there I wonder?

  10. #10
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    Cool

    I've had the X galvo collapse when displaying a complex abstract at too high a scan rate with my original DT-40's. In fact, there was an image in the original version of my "Pop Music" show that would kill my X galvo each and every time I played the show, so long as the speed was at 30Kpps and the scan size was set to anything above 20%. I finally deleted the image from the show to prevent it from happening.

    The only way to get the X galvo to come back was to kill power to the scanner amp and then power it back on. When I did that, it would come back on just fine and continue to perform just fine. But it only took about 5 seconds of displaying that one file to cause the amp to drop out again.

    I haven't tried that pattern with the DT-40 PRO's yet, so I don't know if it will kill them or not. (my guess is, not.) I believe that the cause of the problem is some sort of built-in over-current protection on the amp that cuts it off. That, or else it's a safety circuit that kills the amp if the galvo lags behind the points long enough and with a large enough error... I dunno for sure, but I know that I can reproduce the problem at will.

    EDIT: Ok - I just watched your video, and yep; that's the same behavior I experienced. Except that once my X axis collapses, I have to cycle the power to the amp to get it back. (A quick down and up is all that is required - less than a second total.)

    Adam
    Last edited by buffo; 01-13-2008 at 03:33.

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