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CM3 & Boxypixel - Pressing buttons dims display
#1
Hello,

I built my CM3 with the Boxypixel shell some weeks ago and it worked very well for multiple weeks.
Recently I noticed that pressing the B button (SNES layout) dims the display while holding that button.I didn't care too much and haven't had time to actually look at this so far.
Right now I'm travelling and I've noticed that the effect has increased:
Pressing B now turns down the brightness so much that the display is pretty much just dark.
Also slightly pushing down (in the direction of the backside) on the headphone jack turns the display back on. Pulling it up turns the display down.
I suspect there's a short somewhere and I'm trying to run down the battery right now as I'm unable to open it while travelling.
Any ideas what could cause a short there?
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#2
My first reaction is to check item #6 at https://www.boxypixel.com/pages/assembly...erry-pi-cm
You can see the photo from that step here:

[Image: unnamed_large.png?v=1559586202]

In fact, I would be more suspicious of the similar area shown here:
[Image: IMG_4464_large.jpg?v=1557744416]

Just under the pins marked 44 and 45 are the resistors that control the backlight.  If those were to contact the shell, it could result in the behavior you mentioned.
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#3
I would also look at #4 from that page and tape this area.  That's not likely to affect the backlight, but it can be a problem area if it contacts the metal.

[Image: IMG_4458_large.jpg?v=1557743786]
Card Fighters' Clash 2 English Translation ( http://cfc2english.blogspot.com/ )
Neo Geo Pocket Flash Cart and Linker Project ( http://www.flashmasta.com/ )
Avatar art thanks to Trev-Mun ( http://trevmun.deviantart.com/ )
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#4
I ran into a similar issue but mine was related to the headphone jack. Whenever I would plug in a pair of headphones the screen would occasionally go dark. I found that I could make it happen by applying a tweaking pressure to the plug.

I took the unit apart and reseated the display ribbon into the connector on the board and that fixed it. It must have been slightly loose or misaligned and the small flexing of the circuit board would cause it to lose connection.
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#5
Yeah, krisyadao has a good point. If the ribbon isn't well seated, this flexing can cause connection problems. The backlight is likely where you would notice it first.
Card Fighters' Clash 2 English Translation ( http://cfc2english.blogspot.com/ )
Neo Geo Pocket Flash Cart and Linker Project ( http://www.flashmasta.com/ )
Avatar art thanks to Trev-Mun ( http://trevmun.deviantart.com/ )
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#6
Just came back from travelling and found all these very helpful answers. Thank you!

I suspect that these resistors were responsible. Everything else was neatly covered with tape.
I've covered them now and will see if the behaviour repeats after a while.
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