It’s only rhythmic in that video. It’s not normally.
Still, a distinct repeat of a pattern, even once (I’d venture to bet it does it more often than you’ve noticed) would indicate a cycle of sorts, something resetting or initializing or shutting down over and over, as opposed to completely random source.
Just a clue possibly, that’s all.
Swapping the board definitely did the trick.
@profezzorn if this is something you want to do a postmortem on let me know and I can mail it your way. If not I’ll try the resistor trick. If it doesn’t work I guess I’ve got another test rig board. ¯_(ツ)_/¯
I would be interested in hooking up the 5v pad to an oscilloscope and see how well it fares. This could tell me if the problem is with the amp itself, or if it’s the 5v input that is not working well.
PM me your address and I’ll send it your way then. If I use it for anything it’ll be another boxxie and I’m not in a rush to build another of those.