I ordered a new replacement today from Sweetwater just in case...I can return it if not needed.
Called the Mackie Tech line, spoke with Jordan who was very helpful. I had done all the stuff he was going to suggest. He was thinking it could be a cable that came loose inside, but getting inside is not easy.
Tell me more about your used DL1608. Send info to me on my email: Nielsen at Bloomer dot net. I need the 30 pin connector as both my iPads use that connector. I would move this 30 pin over to the new one, if I go that route.
Perhaps I send this one back to you to perform an autopsy and perhaps find a fix so I end up with a back up unit.
Thank you,
John