SOLVED LCD losing contrast over time

Discussion in 'Calibration, Help, and Troubleshooting' started by orcinus, Jul 6, 2016.

  1. orcinus

    orcinus Well-Known Member

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    I've mostly been doing 5-6 hour prints tops, so haven't really noticed this until now, but...

    The RRW graphic LCD included with the BigBox appears to have one big bug - the longer it's on, the lower its contrast gets. I've been running several 8 hour prints back-to-back and after the first one, i had to tilt my had almost level with the printer bottom to read the display.

    I'm nearing the 16 hour mark now and the LCD is nearly completely unreadable.

    If i were to guess, i'd say that either the contrast trimmer, or some resistor on the board results in such a drift in the contrast control voltage that it makes the LCD unusable after a few hours of work (and, say, 10 degrees of temperature differential).
     
  2. Ephemeris

    Ephemeris Well-Known Member

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    Are you saying the contrast has decreased over time, or that the contrast decreases during a run but then recovers after the machine cools down and powers back up?
     
  3. orcinus

    orcinus Well-Known Member

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    Hopefully the latter, as i don't know what would cause the former.
    But i won't know for sure until this run is finished and i can let it cool down completely.

    This is what it looks like currently:

    [​IMG]
     
  4. mike01hu

    mike01hu Well-Known Member

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    That's looks like a LCD failure and will have to be changed.
     
  5. Henry feldman

    Henry feldman Well-Known Member

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    Looks thermal in nature. I've overheated some of the hats and shields on arduinos/rpis and they get like this... Probably defective.
     
  6. orcinus

    orcinus Well-Known Member

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    Turns out the voltage on the trim pot drifted. I'm not sure how or why, but i'm guessing it was thermal in nature.

    I opened up the panel cover, readjusted it and now it's back to where and how it was.
    The interesting bit is, now it takes just a micron of travel (not really, but a very very very very tiny movement) to go from "can't see anything" to "contrast perfectly fine". And no, i'm not talking normal range of a few degrees - it's an insanely small range. Just bumping the trimpot with a screwdriver will get it into the "can't see anything" zone.

    Oddly, the other direction of the range is still normal.

    I'd say it's a faulty trimpot and it either went "off the rails" due to thermals, or due to vibration.
    Going to continue printing for a few days non-stop now i've re-set the contrast and see what happens.
     
  7. elmoret

    elmoret Administrator

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    I've had the same happen, when I got in to adjust the trimpot I swiped it back and forth several times to clean it. No problems since.
     
  8. Dr Jeep

    Dr Jeep Well-Known Member

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    Mines been left on for a week plus before without this problem so definitely something amiss
     
  9. jet

    jet Well-Known Member

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    I leave mine on for a day or two at a time and have also had zero LCD problems.
     
  10. K3LAG

    K3LAG Active Member

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    Mine is on almost continuously and I have had no issues.
     

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