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Thread: Modules staying on even with ILDA disconnected?

  1. #1
    Join Date
    Aug 2013
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    Melbourne, Australia
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    Question Modules staying on even with ILDA disconnected?

    Hi all,

    I've got a 5w RGB unit on my bench today. So far I've done a bit of troubleshooting and fixed a few things here and there.
    The primary issue it was brought in for though is for some reason the Red and Green modules seem to stay on at full power even with no ILDA input, and don't respond at all to ILDA (Scanners work fine so and checked output on another unit so ILDA ouput is fine).

    So far I've open circuited the input to the diode in case there was a short somewhere, as well as running an extra ground to test but no matter what i do they wont turn off.

    The Blue's also not outputting at all, but that could be a different problem all together so will cross that bridge after i fix this issue.

    Anyone had a similar issue or have any ideas for this weird one?

    TIA

  2. #2
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    Hi Elektryx,

    You've probably got a floating ground that's causing the modulation on the red and green to be getting some power. Test the modulation on those lines without sending an ILDA signal to it and see if you have >0 volts. Assuming so, you've got to start looking for the source. In my experience, such issues frequently stem from a PSU that isn't grounded or is otherwise malfunctioning. If you have multiple PSUs, you can start disconnecting one at a time to see if you can identify the culprit.

    I don't know about the blue. Perhaps you can give it a 5V modulation from a DC transformer to eliminate potential connection problems?

    -David
    "Help, help, I'm being repressed!"

  3. #3
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    In order to help...Which is that 5w RGb module Brand/provider? have pics of driver? If chinese look for driver switches...maybe is on full-power mode, you should switch to ANG

  4. #4
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    Also check the driver bias adjustment

  5. #5
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    Apologies for the late reply, i put it off for a few months as i couldn't figure it out.

    They are the famously terrible LanLing L5459RGB... I know, i know, but i need to get these units working for a friend before New Years.


    So I've already had similar issues with another 4 identical units previously, to which my working solution was to rip out all the Chinese "DMX" garbage PCB's and just hook up each diode, scanset etc straight to the ILDA pins. This has always worked well and the units never give me trouble again.

    However - This 3rd pair of matching units have been a real pain in my ass. No matter what i do i can't get the Green or Red diode to turn off.
    The only difference with this pair and the other 4 units I've fixed is the others have been analogue modulation. These are TTL.

    So far I've tried -
    - Open circuiting the modulation input to the driver - Still stays on
    - Grounding one leg of the modulation wire at a time - Still stays on
    - Separated all power and signal wires from the drivers and tried one at a time on a separate 240v feed outside the laser - Still stays on
    - But finally the only thing that turned it off was to short the signal + and - together... This is obviously not the solution but it shows that it's reacting to some form of input.

    After that i thought i'd measure the two wires of the drivers modulation input, to which i got exactly 2V DC (There shouldn't be any voltage on the input to the driver?)
    This might be a clue for some? Induced voltage inside the driver and tipping the TTL switching threshold? Some other form of driver input other than 0-5v? Differential?

    Need to get these things out the door as soon as possible so any help or advice would be greatly appreciated!

    20171212_194116.jpg
    Last edited by elektryx; 12-12-2017 at 01:45.

  6. #6
    Join Date
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    Hey elektrx,

    In my experience, such issues are often caused by a bad or ungrounded PSU. I'd check those out - eliminating one at a time.

    -David
    "Help, help, I'm being repressed!"

  7. #7
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    Thanks for the reply David.
    I've just completely removed the green driver and module out of the laser. I've opened the driver and wired in a brand new 12v psu, still the same problem..

    It had to be the driver board itself. The only info I can get off it is its a "Mingnuo-12V-10A". Tried googling the hell out if it but came up with nothing as expected. I've emailed a mingnuo company off Ali asking for some documentation.. Long shot I know, but worth a try.

    I feel like there must be an issue with the power side of the driver and its back feeding and giving a false 2V on the modulation input.

    Strange considering its both the green and red modules with the same problem...

    Any other ideas??

  8. #8
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    Check the bias pots.

  9. #9
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    Quote Originally Posted by kecked View Post
    Check the bias pots.
    Thanks Kecked.

    Haven't delved that deep before.
    Do you have any documentation on the process? I haven't found much on google so far.

    Only pots i have are standard 10 turns labelled "W1" "W2" "W3" and "W4".

    20171215_164952.jpg

    Thanks!

  10. #10
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    That board is a mess. Horrible assembly. Might try cleaning all the dirt and flux off. That could be a short anywhere from the look of it. I can't tell from looking what is what.

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