Recently purchased an open-source version of the RetroTink Ultimate from Castlemania. I have an RGB modded TV, and before connecting I use a voltmeter to check the output voltages. The R/G/B lines are the correct voltage, however sync was TTL level. I'm using an RGB → RGBHV breakout cable, I measured both sync outputs, and they are 3v & 4v. The composite sync switch doesn't appear to do anything.
Do I have a defective board, or am I doing something wrong? I don't want to fry the jungle chip with TTL sync...