Solved! TV Sound Setup: Mixing HDMI Input and RCA Output

[TvTroubled]

I'm at my family's home for the holidays and trying to do a little tech support...

Their TV is a Sharp Aquos TMAN-A043WJZZ (see manual here). They use a Roku stick (via HDMI) to watch everything (no cable box) -- this all works fine using the TV's own speakers.

Now, they also have an old Bose 3-2-1 Home Entertainment System (see details here). When they had an older TV and a cable box, they could use this as the general sound output for the TV -- this would have been with RCA cables, not HDMI.

I've been fiddling with various menus on the Sharp TV, but I can't seem to get this audio setup working:

Roku (HDMI) ----> Sharp TV ----> Bose (RCA)

Is this technically feasible? I'd love to know before throwing in the towel and helping them upgrade to a modern sound system.

EDIT: I can't leave a problem unsolved, so I poked around a little further. I suspect the real issue is that the TV only supports digital audio output (documentation doesn't make it explicitly obvious to a layperson like me), so I would need a digital-to-analog converter if I wanted to pursue this...

 

[TvTroubled]

OK! Solved my own problem

Here's how I did it in case anyone else has to do this:

The backpanel of the TV includes a 3.5mm audio jack (center-top here). I happened to have a 3.5mm to RCA adapter (like this) -- I connected the 3.5mm male input into the TV and the RCA male outputs to the "aux" audio ports on the Bose player.

On the menu configuration side, I first turned on the Bose and set it to "aux". This alone will cause the audio to be output through the Bose, but the TV speakers will still be on. To fix this, I opened the Sharp menu, went to System Options > Input Terminal Setting > Output Select, and changed the value from Fixed to Variable.