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Thread: Scanner Testing/Issue

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    Default Scanner Testing/Issue

    Being relatively new, this COULD possibly be found somewhere in here but, I haven't come across it yet.

    Recently bought a nice 2.4 RGB from a member here with DT40 pros and, 18 minutes into watching some shows, the X scanner has appeared to die on me. I'm not faulting the seller, I think it's just bad luck and timing. Wasn't doing anything particularly weird. 30kpps and varying between about 70 and 100% scan angles depending on whether it was a graphics show, a beam show or a Pangolin test frame. I don't believe there are any wires that loosened up in shipping, or at least none that I can identify. The LED's on the amps are lit.

    Any suggestions on step by step testing? What usually goes bad? Is it the (forgive my ignorance) round cylinder thingy (technical term) with the mirror attached that runs through the scanner block or, is it more often a problem with the amp? Can I safely switch the Y axis and x axis cables just to see if the mirror moves to eliminate that as a possibility? If it IS the round cylinder thingy, can just that be purchased and replaced and re-tuned or, am I looking at buying a new set of scanners? I have another set of DT40 Pros that I could pillage if I just need to swap out a part for the time being.

    As I said to Buffo... I spent $233 per minute of pleasure so, it's I guess it's kinda like the average cost of sex. I'd just like to see if I can get this sorted out without having to wait until SELEM and take up someone elses precious time looking at it for me.
    Last edited by Bradfo69; 06-09-2011 at 06:43. Reason: spelling

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    While I'm nowhere near an expert, from what I've read the galvo's themselves don't usually fail suddenly. Usually it's the driver that fails.


    Do both galvo's move to home position when you power up the scanner, or just 1? Home position is usually 45 for both mirrors(at least for both of my PT's, I don't know about the DT's)

    I don't know what other systems are in your projector to give much more input.

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    I would guess this is your problem...

    30kpps and varying between about 70 and 100% scan angles depending on whether it was a graphics show, a beam show or a Pangolin test frame.
    Think about it, your scanners are rated at 40kpps at 8 degrees doing the ILDA test pattern (reasonably complex frame).

    Although you have reduced scan speed by 25%, you are running many times 8 degrees even at 30k (what is full angle, 60 degrees roughly, so 70% is approx 40 degrees?), and so you are subjecting the scanners to significant stress.

    Out of interest, are they running big mirrors too?
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    The Y axis scanner moves to the home position, the X axis scanner doesn't.

    @Norty -

    Maybe I need to get a brief lesson in terminology and angles/size etc. I use LD2000 and Showtime. When I fire up the laptop and start the program, in "projector settings", one page allows you to change the scan rate which it always defaulting to 30,000pps. On another tab it allows you to change the image size, which always defaults to 100%.

    I ran shows on several projectors (all cheap chinese...and a couple Laserworlds come to think of it.) for a long time without ever knowing those settings even existed. For sake of reference, I think they all have crappy 25k scanners. I think the first thing I discovered was how to change the image size by using the sliders to reduce it down to what would fit on the wall. (Usually a distance of about 45 feet away on a 14' high wall I play the image about 9-10 feet tall.) Prior to that, I think I was just moving the projector closer to the wall. Somwhere along the line, I also learned about occasionally slowing the scan rate down if I wanted text or the sharpness of an image to be a little clearer. For beam shows, I never bothered to adjust it and just left the settings at 30k and 100%.

    So... are you saying that in order not to kill scannners that I need to use the sliders to reduce the image size down to something like 30%? That's going to end up making it display about 2 feet by 2 feet, right?? Even if the projector has it's own built in frames that can be sound activated or controlled with DMX they are all larger than that! I know if I reduce the ILDA test pattern down that small, you can't even see the details in it to know if it's right or not. (Although, I know the test pattern should be judged at a much closer distance than 45 feet. - I forget what it is though.)

    I would have thought that a 40k scanner would have an easier time of it that the cheap 25k scanners. That's what I'm not quite understanding. I didn't do anything really different with this projector than I've been doing with the others for nearly a year.

    Somewhere here I think maybe I'm missing something. (I hate only being able to manage to get to one LEM a year!!)

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    I think what we don't know is what the scanners are adjusted to for full scan angle. Your 25k ones may have been at 40 degrees at full angle, whilst the DT's may be 60 or larger. This is all set on the drivers.

    In the software, the main projector settings are usually set for full angle scanning for best performance in beam shows. This is basically the place to set the absolute max size.

    Typically, you would then use the projection zones to set your required angles for the projected material. So the graphics zone would be set smaller, whilst overhead beams, aerial effects, etc might still use the full angle (as defined in the projector settings)

    Now, I don't own DT40's but I do own 2 sets of DT25 and 1 set of DT30's and I run full angle at 100% in projector settings and at 20k speed. This is fine for beams but if I run graphics over 50% size then I get 2 things - distorted images and noisy galvos. This says to me I'm over the limit - the galvos are simply not able to control the mirrors accurately. Typically, in a (my) show situation the graphics zone is quite small anyway as it is targetting a screen or scrim.

    Whilst I cannot say definitively, I think others here would agree that doing graphics at 30k and 70-100% of full scan angle is going beyond safe limits.

    Hopefully some more knowledgable people will be along to confirm/deny what I've said, but it feels 'not right' to me.
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    I have seen some users run their scanners at 100% full angle in software but the full angle on the drivers has Ben turned down. My DT40s are run at 15 to 25% full angle I software which is 10 to 15 degrees. 15% for graphics, 20 to 25 for beam shows. When i tuned my DT40s last, I set my driver scan angle to 20 degrees at 30% software scan angle because that is what I run my CT6125s in my Kvant at.

    You should measure you driver scan angle and derive your software percentage from that. I would not go too far over 15 degrees with beams and 10 degrees with graphics, but would also check your scanners with the ILDA test pattern once you get your X issue resolved.

    For that, swap cables between scanners and turn them on without scanning; see if the X goes to it's home position. If it does, I bet your Y galvo didn't and it is the driver/amp also, vice versa, if the X doesn't go home and the Y does, it is the X galvo.
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    Quote Originally Posted by Bradfo69 View Post
    Any suggestions on step by step testing? What usually goes bad? Is it the (forgive my ignorance) round cylinder thingy (technical term) with the mirror attached that runs through the scanner block or, is it more often a problem with the amp? Can I safely switch the Y axis and x axis cables just to see if the mirror moves to eliminate that as a possibility?
    Hi,

    I've recently had the same problem with a brand new pair of PT scanners. The problems described above are certainly possible causes (not in my case though).

    I would suggest the following steps...

    1. Swap the X and Y signal cables from the ILDA breakout to the driver boards. Does this change the axis at fault? If so problem is likely to be between the DAC and the driver board.
    2. Swap the whole cable between the driver boards and the galvanometers. If the problem shifts axis then the problem is with one of those cables.
    3. Change your software's size and speed to something low and have a simple shape playing e.g. circle. Swap one end of the cables between the driver boards and the galvanometers. If the problem shifts axis, there is a problem with the driver board, if not, there is a problem with the galvanometer. You should generally not swap these around, particularly when running at full speed and size, as the driver tuning is matched to the galvo - keeping it stable. That's why I suggest lowering these and using a circle to avoid any major issue. Be ready to pull the power just in case a scanner goes crazy/unstable.


    Make sure you have powered down the scanners between each change of course!

    Quote Originally Posted by Bradfo69 View Post
    If it IS the round cylinder thingy, can just that be purchased and replaced and re-tuned or, am I looking at buying a new set of scanners? I have another set of DT40 Pros that I could pillage if I just need to swap out a part for the time being.
    You can do this, though you'll need to tune any mismatched scanner from the start of the process described by Adam's guide. Worth doing to give you a good idea of the relationship between the driver and the galvo and the concept of "stablitiy" I refer to above.

    Let us know how you go.

    Cheers,
    Tony
    Last edited by taggalucci; 06-09-2011 at 15:05. Reason: Added extra stuff...

  8. #8
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    what you should do is leave the image scale at 100% and reduce the projected image size using the projection zones. This will allow you to define the exact area where the scan will fall in size shape position and rotation (and myriad other parameters that I wouldnt worry too much about right now). Zones are an extremely powerful feature of Pangolin software and getting to know how to use them is essential. I would recommend using the following proceedure for zone set up.
    1 select the zone you wanna output to and go into the geometric correction.
    2 reset all items - that way there will be nothing left to chance from last time you were in there.
    3 select the size sliders for x and y in turn and reduce to 20-25%
    4 select to output one of the test patterns to your zone - simple or grid test pattern
    5 go back to the geometric correction and use the position and size sliders to juggle the pattern into the place you want and to the size you need.
    6 save the settings and enjoy the shows!

    As for the scanners if the motor is not returning to center on power up then there is no power to that motor.....Look on the scanner driver board - close to the edge just below where the cable connects to the scanner motor there will be a brick red coloured cylindrical component. this is a fuse. If I were you I would pray that its that that has blown - it should have protected the scanner motor but you can see by removing it - may take a little effort as there is often some glue there to tack it in place - and test it on a continuity tester. If its dead then you need to offer a virgin sacrifice in thanks and replace it. If you get stuck for obtaining one let me know and I will send a couple to you for the cost of postage.
    If its not popped - ie the continuity tester beeps it as good then you may well have burned out the scanner motor. There is a lesson in here - it could be a hard lesson but I hope you learn by whatever you discover.
    Rob
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    Thanks all. More learning to do. I won't get much of a chance to tackle the suggestions until early next week though. Next two to three days at work will be super busy and LONG days!

    Rob...you worked on this projector within the last couple weeks. So, you may know how tricky it will be to get at that fuse! If it were only the Y!

    I'm torn though....I'd really like to hang onto the virgin if I had one available.

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    ya just for reference 100% in pangolin is NOT 100% scan-angle... thats 100% output.. scan angle will depend on what the amps are tuned to...

    for example on my scanners 50% on pangolin exceeds the rated scan-angle

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