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Pixel Gremlins.... Need help/advice


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Hello everyone.. hope your setups are going well...

After 3 straight days of rain I finally got my display up and running... HOWEVER.. I seemed to have upset the gremlins by getting them wet ... (bad movie reference...sorry) ..

Here is the issue. My Merry Christmas sign is setup using 2811 30mm pixels on a dot matrix like grid to spell out the letters. Merry is on Univ 3 and is defined as 1 to 80 pixels. Christmas is on Univ 4 and is defined as 1 to 139 pixels. . The controller is a J1Sys P2. All output from the P2 is coming from physical output port 1.

Before I get into details let me ask this... Can one pixel with a problem affect other pixels down the line? The 10th pixel (Univ 3 - chan 28,29,30) in the string (a pixel in the "M" in Merry) is consistantly dead on the red channel. I am seeing some odd behavior in two other pixels in the Christmas string (the letter A and the last S) but they are on Univ 4 pixel 16 in the Letter A chan 364, 365,366 and Univ 4 pixel 1 in the last letter S chan 373,374,375.

In the last "A" in Christmas, there is one pixel that until I started testing never appeared to have a problem. Using XLights (2012b) if I bring up background only in red, all the pixels in the letter "A" light up. But.. if I do a red background and green single pixel chase across it, when the green passes over this particular pixel it will light green but when the chase moves to light the next pixel green, the pixel with the issue does not go back to background red. However, as the chase moves on, it may or may not light back up red.

In the last letter "S" there is one pixel that appears to have had the red LED's fail. BUT... now all of a sudden with the pixel in A failed.. the pixel in S suddenly has started working on red.

Honestly, I'm not sure I have even explained all the combinations of when it seems to work and when it doesnt. The ONLY constant at this point is the dead red channel in pixle 10 on the letter M.

I have tested with xLights 2012b, LOR and the onboard test pattern from the P2.

With xLights, the problem seems to move around (I'm not sure I completly believe in xLights. I have seen screwy things when testing in the past)

With LOR (and this is crazy) when I run my sequences the only bad pixel in Christmas is the 1st pixel in the last "S". The "A" is/was fine. In this new test sequence, I did a red only loop of 5 seconds 100 times and NOW the only dead pixel in Christmas is the one in the "A".

Using the P2 test pattern, the only dead pixel in Christmas is again the same pixel in the A. For some reason the pixel in the "S" is working...
I would like to track it down, but I'm wondering if the best bet is just to replace the 3 pixels, starting with the first known bad one (first in the chain) in question and see what happens... (?)

Any thoughts, suggestions or trouble shooting techniques?




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I just realized a potential/possible STUPID mistake... I went out to replace the one pixel that I knew was always bad and when I went to plug in my soldering iron, I realized that the AC power to the 12V/12.5amp PS does NOT have a ground.


I seems I grabbed a 2 wire extension cord that I had to make the power cable and never gave it a second thought. I looked on the PS and YES there is a place to connect ground.

COULD this be a source of bad behavior even though the P2 and power to the pixels is all 12V DC?



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The answer is maybe. Depends how the supply was designed. That third wire is usually there for safety. If the neutral parts, current can find its way to ground through that ground wire instead of your body. :blink: My PS came with only a two wire power lead, but it's in a plastic case so no real shock hazard.


Worth a try correcting that though.

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I followed the quit mucking around and just replace them advice and it appears all is well in Christmas Town.


They say that curiosity kills the cat .. in my case curiosity puts me WAY behind ...


New motto for the moment... Fix it and move on.. if it happens again .. find out why ..


Thanks ShellNZ ...



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