Some good news on my side. I was able to successfully test the GR79xx board.
Here's a picture of the GR7915 (left) next to the GR7815 micro (right).
I've only tested against my DC shop supply but it performs as expected so far
Try reversing the cables going into the switch to see if the problem follows the cables.
Also, have you tested both channels of the app to make sure they are working correctly.
Ooh... A laser So nice! Can’t wait to see some pics.
I was thinking something different for the brush. Let me see what you’ve come up with before you bother sending anything. I can probably just get it locally if it’s what I think. Thanks though.
Try looking at a scope to see if the noise is on the + or - leg of the channel. This helps to identify where to put your attention.
Good luck and above all, enjoy