i have 8 chuavet color changers,4 martin scx 600 scanners and 2 tree dimmers all on the same data stream and the last dmx assignments,which are 2 color changers seem to lose tracking. they seem to work just the colors dont line up. do i need an opto?

do u have a terminator on the end of the line?

i know how to make one what is the resister i need?

The resistor you'll need is a 1/4 watt between 90-120 ohm.