Does the other EB8 turn on at all? Do you get a light green or orange? Does it connect to Apex? Any specific outlets that don't work? etc. That's what I'm looking for.
Cleaning may or may not solve it. Take a look at an example of what corrosion does to electronics in another one (or two) of my repairs:
My previous electronic equipment repairs Radion XR15: https://www.reef2reef.com/threads/radion-lights-board-level-repair.774331/#post-8197536 A fellow reefer mailed me their Ecotech Radion for repair service as it's long been out of warranty. The unit turns on briefly before shutting down and...
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My previous electronic equipment repair projects Radion XR15: https://www.reef2reef.com/threads/radion-lights-board-level-repair.774331/ Radion XR30: https://www.reef2reef.com/threads/radion-xr30-complete-no-light-repair.792711/ Imagine a problem with a connector breaking off the board...
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EB8 is more basic than EB832 inside, but at the same time, unlike EB832, it does not have a collection of third party power supplies that are relatively easy to diagnose and fix. Inside, everything is mounted on the main board on both sides. So fixing something on that board requires a component level repair. This is something I could do, you'd need to ship it over.