From the Sony website it appears that the Sony STR-DB840 requires the RM-LP204 remote. Here is the link to the Sony website on this receiver:
[Link: esupport.sony.com]You can find a replacement remote for sale via eBay or other replacement remote shops. Here is a website that searches for replacement remotes either by remote model or equipment model and sorts them by the lowest price :
http://ezremotefinder.comGood luck!
