We had our Bose Acoustimass 300 Subwoofer fail and instead of throwing it out, I spent about $5 on a new Schottky Barrier Diode. I think this bass module is the same for the Acoustimass 700 system (700 has a better soundbar than the 300).

if you have any good tips yourselves, please add in the comments and I can add to this description or pin your comment.

pulled the speaker apart to access the circuit board. melted off the hot glue and desoldered the faulty chip.

soldered on the replacement chip and now it works again.

B2100A-13-F SMA(DO-214AC) Schottky Barrier Diodes
I bought it on eBay:
https://www.ebay.com.au/itm/10PCS-X-D...

How to solder diodes and other chips - ShopJimmy video:
   • How to Solder - Beginner Guide to Sol...  

Use this video at your own risk. Don't go zappy, think safety and you'll be happy.