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Thread: LCD Issue.....

  1. #1
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    LCD Issue.....

    So, this was a working HM - and still is aside from the LCD. The left and half of the display seems not to be working and the letters are garbled occasionally and offset to the right half of the display. See the image below:


    This was working originally, and I suspected dry joints so have re-soldered all the LCD connections and the shift-register chip. No real change. I've tested continuity between the shift-register and the LCD pins - all good. I've also tested for shorts between the LCD line pins - all good.

    I've measured the voltages on the legs of the shift register that drive the LCD and can see bouncing between 0-3.3V (well, seeing that on a slow response voltmeter is tricky but I can see changes in voltage).

    Any more pointers?

    Thanks,

    John

  2. #2
    TVWBB Honor Circle Bryan Mayland's Avatar
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    Oof, both times I've seen something like that, I had to completely replace the LCD. I saw Dave on EEVBlog recently repair a character mode LCD like this and he said usually it is because the zebra strip that connects from the PCB to the LCD itself to drive the rows and columns has become loose or become corroded. Have you tried squeezing the LCD's black bezel to sandwich the LCD glass more tightly to see if it helps? If it does maybe you can unbend the black tabs that hold the frame on there and clean it out or maybe just give them some extra bend to increase the clamping force?

    If it were the connection between the HeaterMeter and the LCD, then you'd just get garbled random characters on the screen, or if the connection was poor you'd get some characters being just the wrong letter. I think you're going to need to replace the LCD though. :/
    I'm that HeaterMeter guy what ruins everybody's free time.

  3. #3
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    Thanks for the response. I'll be looking to replace the LCD in the near future.... it still works perfectly well headless!

    Cheers,

    John

  4. #4
    TVWBB Honor Circle Bryan Mayland's Avatar
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    Nice! I pull the LCDs off 4.3 boards all the time when testing them so this is something I will always keep working (the headless design). If you're going to replace the LCD, I can get you one at cost with a new strip of 16 header pins (which is currently $7+shipping ~$4). I only have white FSTN+ now since that's what goes in the kits, but I think it is the best looking. I'm heatermeter@capnbry.net if you ever want to put a head back on it, but definitely try giving it a push on the black bezel to see if the connection inside just has accumulated crud or something.
    I'm that HeaterMeter guy what ruins everybody's free time.

  5. #5
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    Bryan - truly appreciate the offer for an LCD but had already dived in and bought one (well, five actually) as I found some NOS on Ebay for a very fair price. One for me and the rest for future HMs

    I did separate the LCD, along with the zebra strips - everything looked pretty clean but when reassembled, it was still the same problem. Given that the shift register seems to be working, it is just likely that this LCD board has died in some way. I have two HMs and this was the first one that I built from around 3+ years ago.

    Cheers & thanks for all the hard work.

    John

  6. #6
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    And just to wrap this one up, new LCD installed and display works perfectly. Chalk this one up to a bad/dead display.

    Cheers,

    John

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