Still nothing. I tested my display with my 450 and the same cable/adapter, that worked fine. I have a MacSD in that machine and noticed the leds on the MacSD on boot, there was a cycling then normal start. On the 475, nothing other than power and termination ever lit up. We aren't getting to scanning for a boot device. Based on this
https://macgui.com/news/article.php?t=496 and the assumption that the startup is more or less in the same order for the 475. "Let's take stock of what has happened thus far, if there have been no errors. The screen is black. The VIA was initialized. We heard the boot beep. The IWM was initialized. ROM was check-summed and the RAM was tested." So based on that something isn't allowing us to move forward with start or something isn't getting initialized correctly.