Troubleshooting Time Capsule configuration

I have a 4th gen Time Capsule (A1409) and it's has wifi issues. I'd appreciate help figuring out what's wrong with it. It's been working pretty well over the last couple years (I think I've had it for 2 now; bought it refurb'd from Apple), but the wifi started crapping out a couple days ago.

My set up is pretty simple. I have Comcast internet with a Motorola SB6121 modem and the Time Capsule is connected directly to that.

Yesterday, after having the wifi connection drop several times in a row (tried reconnecting on my MBP, but it told me it couldn't connect), I tried a hard reset (held reset button down until light flashed amber). I first tried setting it up with a new configuration, no go (unknown error occurred). Hard reset again, tried restoring network settings, no go. Did a factory defaults reset (held reset button while powering on until light flashed amber) and after going through the steps of setting a new network name, the Airport Utility (6.3.6) tells me an unknown error occurred and it can't continue.

I think when I was troubleshooting yesterday a wired connection from the TC to my MBP was working (before I reset anything).

Any ideas what to do next? Is it possible there's a specific order to configure the TC (as in, reset it, configure it, then connect to the modem?)?

Any help would be appreciated.

Thanks!

Seth

 

Ok. I'm a cheapskate. Maybe I'll buy one off Craigslist/eBay with a borked HD and swap parts.

Thanks!

 

Really? I didn't know about that. Unfortunately, my extended AppleCare ran out already. ☺

--- Post Merged, Apr 11, 2016 ---

Yeah, it should have been ok. The modem was close to it, but it wasn't enclosed or covered.

Thanks!

 

Ok. I generally buy refurbished. Can I plug in a hard drive?