• Registered: 2011-03-21
  • Posts: 29

Topic: C8 touchscreen intermittent

I recently got a used C8.  The touchscreen is intermittent.  Here is the history.

1.) The first time I powered up, it got to the network screen. I entered my network password, but noticed that screen calibration was off. e.g. if I typed "r" the display might say "e" and so forth. But the network eventually did connect. Then when I got to the activation screen, it would not respond at all.

At that point, I thought I'd try to power cycle it.  It went past the various logo screens, briefly displayed the "network connected" screen. And THEN got to the activation screen, which again would not respond.  I repeated this sequence several times, always with same problem.

2.) I tried "special options" procedure. I got to the touch screen calibration. I touched the four corners and center targets. As soon as I'd touch one, the next one would appear. So it seemed to know it was being touched.

After touching the center target, I got to the "drag the blue ball" test. I was never able to get the ball to move out of the first circle! I tried my finger with varying amounts of pressure. I tried the rubber eraser of a pencil (thinking it was a smaller diameter so maybe more accurate to read). No luck. No matter what I did, I couldn't move the ball.

On that same "ball check" screen there is a button in the lower right that says "retry." Pushing that also did nothing. The button, the blue ball, and the two circles, all remained on the screen. Eventually (after maybe 30 seconds) the screen clears and goes back to the first target in the upper left corner.

I've repeated this sequence several times, always with the same problem.  I'm guessing that either the screen is not calibrating correctly, is outputting wrong data (e.g. some area of the screen is "stuck"), or else is not passing its data to other parts of the firmware except for the calibration screen.

Any other history similar to this?  Any suggestions?  Thanks in advance!

2 originals (+1 fried original), 2 C1s, 1 Infoseek8, 1 semi-functional C8
  • Duane
  • Duane
  • Blue Octy
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  • From: San Diego, CA
  • Registered: 2006-08-24
  • Posts: 8,209

Re: C8 touchscreen intermittent

Try using a fingernail or the point of a pencil.  This is a resistive touchscreen, so works best with the smallest area of contact possible.  This is unlike the (now) more common capacitive displays where you use the pad of your finger.

Resistive touchscreens use a couple of very thin layers of plastic that touch when pressed together.

It's also possible, of course, that the touchscreen on that unit is damaged.

Duane's Website

  • Registered: 2011-03-21
  • Posts: 29

Re: C8 touchscreen intermittent

Thanks very much for your reply, Oh Lord Chumby!

I didn't try a pencil point, but I did try the hard and rather pointy end of a Bic pen cap.  Also tried a fingernail.  In both cases, I got the same result as with my fingertip or an eraser.

I do note that when I manage to get into the calibration mode, just a very slight gentle press by a fingertip is registered (causing the given target to disappear, and the next target to appear).  So at least in this case a fingernail or pointed stylus is not required.

The previous owner told me if something (dirt, etc.) gets trapped between the screen and the bezel, that can cause a malfunction.  I thought I'd try removing the bezel to check on this.  I removed all six screws on the back of the unit, but managed only to pull the top of the bezel forward by 1/4" or so.  (I can't figure out how to go any further with the teardown, and didn't want to force anything.)  In this condition, the screen seems to work correctly.  I went through the calibration procedure at least five or six times, and successfully dragged the ball every time.

Do those observations suggest anything else to you?

Do you advise me to proceed with removing the bezel?  If so, what do I do next?  The top is free, but mid-way down the bezel seems to be VERY firmly attached to the rest of the unit.

Thanks again!

2 originals (+1 fried original), 2 C1s, 1 Infoseek8, 1 semi-functional C8
  • Duane
  • Duane
  • Blue Octy
  • Offline
  • From: San Diego, CA
  • Registered: 2006-08-24
  • Posts: 8,209

Re: C8 touchscreen intermittent

OK, so the bezel in the chumby 8 is actually not something that comes off by itself.  The display is attached to the bezel by screws, the part that holds the electronics then attaches to the the bezel, and finally the back is siid over the whole thing.

So, to open a C8, you correctly need to remove the 6 screws - the four covered ones in the corners behind the bezel, and two uncovered ones on the very back.  At that point you should slide the back about 1/4", then gently pry the two side panels outward - there are several little hooks in the side panels that go into slots on the back part.  Once those hooks are out, the back should then easily slide the rest of the way out, and the rest of the disassembly should be obvious.

Duane's Website

  • Registered: 2011-03-21
  • Posts: 29

Re: C8 touchscreen intermittent

Thank you, Duane!  That sounds quite similar to what the previous owner described.  I was unsuccessful with his procedure, but I'll try your procedure with attention to details.  Maybe I'll succeed this time.  Wish me luck ... this is potentially the 6th member of my Chumby family if I can get it working correctly.

2 originals (+1 fried original), 2 C1s, 1 Infoseek8, 1 semi-functional C8

6 Reply by gminpa (edited by gminpa 2020-12-04 20:58:05)

  • Registered: 2011-03-21
  • Posts: 29

Re: C8 touchscreen intermittent

OK, I successfully removed the back.  Those were good, detailed instructions, Duane, thanks!

I now want to see whether anything was pressing on the touchscreen when the unit was assembled.  That might explain why it didn't calibrate correctly when screwed together (but it *did* sense being pressed).

It looks as if the next step is to remove the four screws (two on each side) holding the rear assembly with electronics to the bezel.  Hopefully that will allow me to get enough play between the bezel and display that I can examine that more closely.  Otherwise it looks like a nightmare, with several wires (mic, speakers, etc. etc.) to disconnect ... most worrisome being the flexible connector for the display itself.

Needless to say, this is *much* worse than when I used to work on broadcast audio and video equipment with through-hole components!  My fingers are crossed ...

2 originals (+1 fried original), 2 C1s, 1 Infoseek8, 1 semi-functional C8