Butterfly LCD problem

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steve17
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Posted by steve17: Tue. Sep 25, 2007 - 02:37 PM
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I removed the mega169p from a Butterfly and replaced it with a mega329p. Everything seems to work okay except the LCD.

I can see only one complete character. It's the second (or maybe third) character. It's faint unless I view it from below. When I do view the display from below I can see a few segments of the other characters also.

I tried adjusting the contrast by running the original Butterfly application. That doesn't help. That will only lessen the contrast and that makes it worse.

I've looked at the data sheets for the 169p, 329, and 329p and I don't see any differences.

I've looked at the migration documents also and found nothing.

I may have damaged something when I removed and replaced the microcontroller, but I don't know what it would be. I did not use hot air. I removed the original chip with ChipQuik.

I doubt the LCD is sensitive to ESD but if it is, the pins would be essentially unconnected while there was no ATmega soldered on the board.

It would surprise me if it was that sensitive. I've taken apart other LCD "sandwiches" that were held together with a metal frame. I inspected each layer, put it back together, and it works as good as new.

The "view from below" thing is not new. I bought a Butterfly a year ago that requires me to view it from below. But when I do, the display is good.

This Butterfly that I did the brain transplant on, had a good LCD display before the transplant. I checked it out before the operation.

Any ideas?

Tags:

AVR Microcontrollers, megaAVR and tinyAVR, ATmega16, ATmega169, ATmega32, ATmega329
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steve17
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Posted by steve17: Tue. Sep 25, 2007 - 02:49 PM
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I forgot to mention I used no clean paste flux. There is undoubtedly some flux under the chip. I wonder if the LCD pins are sensitive to that.

I don't know how I could remove the flux. Maybe I could soak the board in flux remover.

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Bronze Marktheusch
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Posted by theusch: Tue. Sep 25, 2007 - 03:42 PM
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Quote:

I wonder if the LCD pins are sensitive to that.

Yes, yes, yes.

Squeaky-clean might/should help, but check the schematics for the Mega169-errata fix as mentioned in
https://www.avrfreaks.net/index.p...
as well. Also
https://www.avrfreaks.net/index.p...

Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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steve17
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Posted by steve17: Tue. Sep 25, 2007 - 04:24 PM
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Thanks Lee. I am checking out those links and will try capacitors.

In the meantime I have a question about squeaky clean. The visible board is clean but the ATmega is a mlf 64. Also known as QFN. It has no leads, just pads on the bottom. Is it possible to clean the flux from under the chip? Do the professionals do that? Can the entire board be soaked in flux remover? I think if the LCD isn't sealed, any water etc. getting in there would ruin it.

I'm a programmer, not a hardware engineer so I have no clue about that.

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leon_heller
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Posted by leon_heller: Tue. Sep 25, 2007 - 04:31 PM
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I use IPA for flux removal, it shouldn't damage anything.

Leon

Leon Heller G1HSM

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steve17
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Posted by steve17: Tue. Sep 25, 2007 - 05:37 PM
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As long as the LCD is sealed, I would think so. Is that "IPA" anhydrous isopropanol? I have the isopropyl but it is 10% water.

I had an experience with an LCD which was probably designed many years ago. I think a drop or two of water killed a few segments.

It was a "sandwich" held together with a metal frame. Somewhere is the sandwich was a glass plate with conductive traces. I think it was metal deposited on the glass and was only a few atoms thick. As I remember, the metal traces were transparent. You had to get the light just right to see them. When I looked carefully I could see a few traces near one end of the glass were discolored or missing. I suppose it doesn't take much to dissolve a few atoms.

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steve17
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Posted by steve17: Tue. Sep 25, 2007 - 05:43 PM
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Well I suppose a soaking could possibly damage the piezo speaker. But I look at it this way. If I want to hear Für Elise, and sometimes I do, I have better equipment to play it :)

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