I'm nowhere near a slot machine right now.
However, I know I did a topic on it and posted the readings I got from that wire.
The way to find it is to go to the WMS Williams Video section of NLG, go up to the search box and type in "printer COM" and a bunch of topics will come up.
Ohh...here it is...lol...>>>
https://newlifegames.com/nlg/index.php?topic=23090.msg173643#msg173643That orange wire between the PSU (Power Supply Unit) and the interface chip on the printer harness, is more of telltale wire...searching for a certain voltage.
If it doesn't find the voltage from the PSU, it tells the MPU to shoot out the "printer COM error" code.
Only way to fix it, is to replace the PSU, or the capacitors inside that relate to that orange wire.
I'm NOT the guy that knows exactly which IC components to replace.
Compare the backplane jumpers too, from the known good cabinet and this one.
The jumpers have to be set correctly.