Led Matrix Doesn't display correctly

[yishi]

Hi,

I have issues with 8x8 led matrix. They are just not displaying correctly.
The three matrixes in the image are running on the same code( example code, matrix8x8).

IMG_20141004_144015.jpg (224.18 KiB) Viewed 336 times

I made sure the address is right. One is 0x75 and one is 0x72.(As you can see in the image).

IMG_20141004_153459.jpg (191.92 KiB) Viewed 336 times

This happened to me before when I made another purchase and got the broken matrix replace.
Did I do something wrong or these matrixes are actually broken? Please help!

[Franklin97355]

If you disconnect the last matrix what happens?

[yishi]

Nothing changed.

IMG_20141004_170209.jpg (874.52 KiB) Viewed 320 times

IMG_20141004_170323.jpg (761.01 KiB) Viewed 320 times

[Franklin97355]

One last test. Try moving one of the bad ones to a different spot on the breadboard (probably won't help but try anyway) If that doesn't help email [email protected] with a link to this thread for replacements.

[yishi]

Thank you! I tried switch positions and still nothing changed. I will send email for replacement.

[hiduino]

It looks like those two matrix are soldered backwards. If you hold up the matrix with the headers to the left the the lettering on the side of the matrix should be facing down. If they are facing up then they are backwards.

[yishi]

Thank you hiduino! I think it is very likely the reason. However, it is very hard to desolder the chip now with solder iron. I ordered a heat gun, hope it can work.

[Franklin97355]

I've used chip quik in the past with fair to good results http://www.chipquik.com/store/ but it does not hold up to getting a new tool ;)

[yishi]

Thank you franklin97355 and hiduino! I figured out the cause is I soldered the matrix backward. Now they are all working fine! Takes me one week to get all my tools though, heat gun really helps, lol.