MAX7219 and Arduino Uno bug

Hi! I have MAX7219 and I controlled matrix and 7 segment display with it and everything worked good. Last week I saw big bug. Some leds on matrix are constantly ON, and 7 segment display won't turn on any segment. I bought new marix module with new ic max7219, and nothing has changed, also I replaced arduino mcu and things are same.

Please tell me what causes that and how I can fix that. I am searching for topics on forums about same problem but i didn't found answer.

Sorry for my bad English.

Post your schematic. We have nothing to review yet.

How are you powering the MAX7219 board? VCC and GND are the power lines and do not appear to be connected in the picture you posted. These must be connected up...

Though you can connect the display signal lines to pins 0 and 1 it is best not to use those particular pins and to leave them for the serial port access so you can print debug messages.

OK so the picture is not representative of your setup… I am surprised the LEDs illuminated at all :slight_smile:

You may find the Arduino or USB source cannot supply all the current needed and that the power rail is collapsing.

Try powering the LED matrix from another power source and keep a common GND.

If you have changed your software or libraries since it last worked then backtrack to your working setup.

Without knowing which IDE, having a full schematic, an example non-functioning sketch and a link to the exact source for the libraries you use then it is going to be guesswork what is wrong with your setup.