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Thread: Can anyone identify this grounding issue?

  1. #1
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    Default Can anyone identify this grounding issue?

    THIS APPEARS TO HAVE BEEN RESOLVED. PROBLEM WAS PROBABLY A SHORT. THANK YOU TO ALL WHO HELPED.



    I have two 7W RGB Goldenstar lasers with a bizarre and unidentified problem (assume it is a ground issue).

    When running each individually, everything works fine. The second I share the ILDA signal in parallel between the two, I get a bright red dot which appears to be about 50% brightness, but that's pretty bright when it's a 1W single static beam. This only happens on one of the lasers, and the static beam seems to swap over depending on the configuration. I am running a laptop which does not connect to AC ground.

    THE FOLLOWING DID NOT HELP:
    - I ripped out all the 'auto DMX' boards and stuff that golden star builds in to their lasers as I thought it was a problem with that.
    - I thought it must be a grounding issue which I still suspect it is, so I rewired according to Bill's guide, and tying all grounds together and NOT connecting pin25.
    - Changing the modulation channel to a different colour (the second the modulation wires come into contact with ANY ILDA pin except 25, the dot appears)
    - Swapping FB3's, swapping laptops, swapping cables
    - Connecting pin25 to the central grounding point

    WHAT MAKES THE DOT DISSAPEAR
    - When I disconnect the ILDA cables on the good laser, the dot goes away
    - When I disconnect the ILDA cable from the bad laser
    - When I remove AC ground from the system by unscrewing the wire from the plug
    - When plugging out the FB3 controller from the laptop USB port, the dot disappears. The second I plug it in again, even if the software is closed and laptop off, the dot appears.
    - I tried switching laptops and FB3's and it made no difference

    This is where it gets weirder....

    I did a test running two separate FB3's to the two separate lasers, giving totally independent ILDA signals.

    I plug in one FB3 to the USB port and no problems. The second I plug in my second FB3 to the other laser, I get the dot again. So if both FB3s are plugged in to the laptop at the same time, I get this dot, but the second I remove one of them from the USB port the dot is gone and the laser that is left plugged in functions fine.
    Last edited by Humphry; 10-01-2014 at 14:35.

  2. #2
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    Default

    Did you eliminate both of the ILDA cables as a source of the problem? Does the problem follow the cable when you're using 2xfb3?

  3. #3
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    Thanks for the quick reply.

    Yea, I have tested the ILDA cables individually and they work fine. The shield is connected to the metal hood, which in turn connects to the case and AC ground. Both sides are like this of the cable.

    The problem is not present when I use the same configuration with different lasers. But that being said, the problem definitely follows the cable in the sense that when I break the ILDA connection at any point, be it at the USB port while leaving my actual ILDA cable plugged into the FB3, or the ILDA cable itself, the problem goes away.

  4. #4
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    Lightbulb

    Hiya Sir H -

    Indeed, 'Ground Voodoo' is the most-perplexing kind.. Here's a few thoughts:

    Quote Originally Posted by Humphry View Post
    - Connecting pin25 to the central grounding point
    First suggestion: Get a 'raw' DB-25 connector (the kind you can either 'insert your own pins in', or the 'solder-cup' style..) and Solder / Pin-up the Ground, on Pin 25, hook that up to the 'ILDA-out' (I'm assuming these PJs have both I and O for 'daisy-chaining'?..) and connect that to *anywhere* on the 'offending' PJ chassis.. The 'goal' is to get that 'last-in-line PJ', to connect 'earth ground' with the ILDA Pin 25.. Just a test.. try it, lettuce know..

    Second: Just to-know, inspect the DB-25 on the *Projector-side*, and see if all the 'color-returns' (–'s) , go to their 'assigned pins'.. Or, of they all just 'tie to ILDA Pin 25.. You can see where they 'should go', in the "ILDA Pins", part of this diagram (ignore the other stuff for the NEOS-side..) http://www.photonlexicon.com/forums/...8&d=1368676419 ..Again, lettuce know..

    Quote Originally Posted by Humphry View Post
    - When I remove AC ground from the system by unscrewing the wire from the plug
    - The second I plug it in again, even if the software is closed and laptop off, the dot appears.
    Two-questions / things to investigate:

    - Do your Laptops (both) have an 'external AC/DC-adaptor / PS', with an AC-plug, then DC-power to the laptop? Or, does the Laptop connect directly to AC? In either case, does the AC-side Plug have 2 or 3 prongs (WITH Earth Ground..) If they do-NOT have a dedicated Earth Ground-pin, I'd suggest trying to connect anywhere on the 'laptop-chassis' (any one of the port-connectors, that might have a 'screw-lug', ie: VGA / DVI-out, etc..) to Earth Ground.. Lettuce know if there's 'any change' with the dot..

    - Lastly, I'd see if you can *verify* that your house / office, or wherever you are testing these, Does, indeed, both have Earth Ground, and that the 'Line / Neutral's are not 'swapped'.. In other words, the 'hot is coming thru the neutral-line'.. There are store-bought testers you can just plug-in and test, for both of these conditions (Good Earth Ground and correct Line/Neutral wiring..) ie: http://upload.wikimedia.org/wikipedi...cle_tester.jpg ..Google search / go to an electrical-supply place, and get one.. Priceless..

    Quote Originally Posted by Humphry View Post
    - I tried switching laptops and FB3's and it made no difference
    ..Lastly-lastly, and just for *'s and giggles, get a piece of wire, and connect the two FB3s *chassis*, latch onto the 'screw lug' for the ILDA-connector.. Lettuce know if the dot goes away...

    ..Hurry up, you don't have much time left!

    cheers..
    j
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  5. #5
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    I can't say I know how to solve it, however I have pretty much the exact same issue with one of my home built projectors. Have tried essentially the same things you have, grounding things out according to the pangolin guide. The only difference being it's my blue rather than red.

    I temporarily solved the problem by backing up my diode threshold setting on the badpip driver so that the diode is off at threshold. At the very least this has brought the intensity down to a barely visible state.

    It's definitely something ground related as lifting the ac ground does solve the problem. But otherwise I haven't been able to figure it out, has been an intermittent problem for over a year now. I'm very interested to see what you find. Next step for me is to disconnect everything and ensure everything is isolated / not contacting the case and then reconnect everything one by one.

  6. #6
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    I had a very similar problem with a 2W green laser coming on as soon as ILDA cable was attached. In my case it was also smoking some other bits, so clearly a short circuit.
    Turned out the +ve TEC drive wire was pinched under one of the mounting bolts for the head, thereby shorting to the baseplate as soon as power was applied (and then subsequently shorting to every other thing with a ground via pin 25 once ILDA cable was connected)

    Took hours to find, and only then discovered by accident. I would say that you might want to strip a number of components out, particularly anything where a wire passes near a bolt. In my case, the wires from the TEC pass out the back of the module where they are sandwiched, so pass very close to the mounting bolts. Check all your heads. OEM Laserwaves seem to all be built like this, and so could all suffer the same issue quite easily.
    Frikkin Lasers
    http://www.frikkinlasers.co.uk

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

  7. #7
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    Hi All thanks for your amazing and fast responses.

    So I opened up the projector and found the Earth wire to be EXTREMELY hot when running. The TEC power is short circuiting exactly as per your situation Norty, I have confirmed this with a multimeter. Am trying to find the problem now. Maybe this will solve my ground issue?????
    Last edited by Humphry; 10-01-2014 at 10:49.

  8. #8
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    I would have thought that suggested a short rather than a pure ground issue with the current going to ground down that earth wire, hence the heating of the wire.

  9. #9
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    I found the short! Those silly laser wave people only put nylon spacers under two of the four screws of the laser head, so the DIODE+ was in direct contact with Gnd/Earth.


    Quote Originally Posted by White-Light View Post
    I would have thought that suggested a short rather than a pure ground issue with the current going to ground down that earth wire, hence the heating of the wire.
    This started off as purely a signal issue that I have been having for more than a year. But I have uncovered a short with the Laser-Wave green head, although the head has never been a problem which suggests that maybe I nudged it into a short while tinkering with the signal issue.

    I am hoping that this will have magically solved my signal issue as well

    Will box up and report back.

  10. #10
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    For all those interested - It seems that I have been living with the short for the entire time. All appears to be solved now but I will be sure to let people know if it persists. Not impressed with Laser-Wave at the moment, but maybe there is some explanation. Everyone makes mistakes from time to time, just lucky it did not cause a fire or shock someone.

    Thank you to all who helped me out - everything was useful and helped me to eliminate things.

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