A very weird digital sidecar problem...

[billbo911]

Without having hands on, this is difficult to help troubleshoot, but what the heck, troubleshooting systems is what I've done for a living for 30+ years.

The very first thing you need to ask is: "What changed between yesterday and today? What was the last thing you did?" That might point you in the right direction. The fact that it was working yesterday and is not today is baffling. Something must have changed. If you can't think of anything at all, try the steps below, maybe you'll find something.

Start by plugging in one encoder at a time. If either one makes you loose the +5vdc, you have narrowed down the cause. If neither does by it's self, what about trying to move them to a different input,. Same result?

If neither kills it by it's self, then maybe the power supplying the board it the issue.