Hi dear community!

I just got a used Sonos Sub off a deal and I knew it is not working when I’m doing the purchase. However, after I got the Sub and did some testing to set it up I realized it is more complicated than I thought to fix it.

So basically the devices just have a white LED constantly flashing, no response to anything, including hold the button to reset. I read from the support page that a constant white LED flash indicates boot failure. There are some interesting symptoms as well: when I connect it to ethernet cable, and search for devices using the iPhone app, it gives “found 0 Sonos product”,(instead of “No Products Found” when it completely powered off), and when I click the Setup button the app just crashes.

So basically I assumes there are some problems in the logic board, since it powers up fine and both boards looks in good shape(it’s already teared down). I have no other clues and searched around the community but can't seems to found any resources. For some reason I am not able to refund this unit, so I am stuck with it, and some how I would like to take the journey to repairs it for fun. 

Just wondering if anyone experienced similar symptoms on the Sub? Or are there any serial debug ports on the logic board I can use to see the boot loader debug logs ?

Any help or chat would be awesome!

Thanks