My school has a LED scrolling display board from long ago in the main lobby. When I flip the power switch, it turns on and starts displaying zzzzzzzzzzz... There's a connector on the outside (2x10 pins, see picture) that doesn't match up with anything I can find at school or online.
I have done some testing with a multimeter. Labeling the top left pin 1, the top right 2, second to top left 3, second to top right 4, and so on, I have done some testing. Pin 1 is connected to pin 2 with a resistance of about 3.7 ohms, while pin 2 is connected to pins 4, 6, 8, etc. (all the pins on the right side) with almost no resistance. 1-2 have a voltage drop of about 4.7 V when the thing is on, and 1 is positive while 2 is negative. All other pins next to each other (5-6, 7-8, etc.) also have a voltage drop, although it is a little smaller. 3-4 has a voltage drop of 0 in either direction.
This testing leads me to believe that the pins on the left are connected to power while the pins on the right are connected to ground, but I am not sure of this. Even if that was true, where do I go next? How can I go from displaying zs to being able to input a message for display?
For reference, the only company name anywhere on the board is "The High School Source Property of MarketSource Corporation 10 Abeel Road Cranbury, NJ 08512 (800) 877-4401"
The board is a matrix of LEDs about 2 meters long and 6 LEDs wide.
Thank you so much for your help. Let me know if you need any more information.