Thank you all for your replies! So it looks like I've got a problem with the SG503 power supply then. Because ~4.74V is probably not enough to power the counters. And the LED drivers require 5.25V per the datasheet I found (could not find a recommended minimum). Guess I need to keep looking. If anyone would be willing to take some measurements (running the SG503 with a TM5000) I would greatly appreciate it!
-Frank
Frank Mashockie