Thank you amigos, all the thanks are to Ricky2001 and his dedication to this beauty
You probably already know about the freeplay EPROM but just in case: http://www.arcadecollecting.com/hacks/tron/
It's the final touch imho
I noticed on the picture below that your machine also has those weird lines on the right of the screen.
My TRON also has them, I thought for a long time that it was a graphical glitch, but apparently "it's not a bug, it's a feature"
Thanks mate, yes itīs set on freeplay too
Right I see we think it was a graphical glitch... Many thanks for the info!