LCD screen lit but blank

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This topic contains 6 replies, has 2 voices, and was last updated by  moshang 1 year ago.

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  • #3754

    Sethinthebox
    Participant

    I’ve completed the build of the TB2 and everything seems ok, except that the lcd screen is lit, brightly, but shows no characters and the contrast pot doesn’t seem to affect anything. I can hear sounds when I hit the keys, the led glows…all seems ok but the the screen. How do I go about troubleshooting it? Any suggestions where to start?

    #3755

    Sethinthebox
    Participant

    Worth noting, I’ve double and triple checked all the solder connections, diode and caps. I’ve hit the reset button a half-dozen times and I’ve recompiled and uploaded the firmware. Again, everything seems ok except the screen.

    #3756

    moshang
    Keymaster

    Hey Seth,

    It could be that your not turning the trimmer far enough. Many people have been caught out by how many turns it requires (a number of complete revolutions).

    It’s also worth checking that the trimmer has the value 103 printed on it. It has happened once before that our supplier packed the wrong trimmer.

    #3758

    Sethinthebox
    Participant

    Thanks Moshang,

    I’ve tried quite a few turns in both directions with no change in the lcd. Is it possible to turn it too much? The trimmer seems to be the correct component. As the backlight is on, it seems I have voltage. I was going to see if I could test data next.

    #3759

    moshang
    Keymaster

    Nope, you can’t turn it too much – the mechanism just skips over the end point on either side.

    You may also need to check the soldering on the Arduino Due’s header. It’s a little harder to check since the solder connections are under the pcb out the lcd. But you can check them with a multimeter if you remove the Arduino Due. To see which pins are connected, have a look at the Fritzing schematic.

    #3763

    Sethinthebox
    Participant

    Just an update…

    I tested the pin outs with my voltmeter and there was definitely a problem with a few of the connections. Perhaps I damaged the circuit board…I’m not sure. I has a bit of thin copper wire around and I was able to run jumpers between the bad connections, reset the circuit board and, viola!, I have a functioning TB2. Thanks for the support. My only issue during the troubleshooting was following the lines on the Fritzing diagram, I didn’t know how to isolate connections or do anything with the program. I was also too lazy to learn šŸ˜€

    Thanks again!

    #3764

    moshang
    Keymaster

    You’re welcome – I’m happy your TB2 is working!

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