Thanks for chiming in. I've already purchased a replacement. I picked up an EA8300. Walmart has apparently been clearing out an older model of the EA8300 for $35. Unfortunately, I didn't get that screaming deal, but the price I got seemed decent under the circumstances. I'm not sure what the difference is compared to the model I got, but the UPC number on the one I purchased differs from the UPC on the clearance models. People are apparently still running across that deal at some locations.
I'm actually using the same power adapter that I was using with the WRT1900AC. I've got all the power running through a CyberPower UPS. I believe whatever happened came through my Comcast cable feed, which I did not have running through the UPS.
I was just curious if anyone ever bothers to get old routers repaired. I'm thinking it might be a good idea to have a backup. I liked the WRT1900AC and I got it for a good price. If I could get it fixed for 50 bucks, I probably would. The internet light is flashing amber/orange, which apparently indicates a hardware issue. Reading through the owner's manual, there may be some additional troubleshooting I can try, but I'm guessing I won't even be able to access the router.