Turn on the TV and set it to the video source to be able to easily see the menus as you set up the dubbing process. Put the source tape you want to record in the VCR. (Copy protected tapes will not be dubbed.) If you want to avoid dubbing from the DVD to the VHS tape, remove the erase protection tab from the cassette. Put a compatible recordable disc (non-finalized disc, unprotected disc) in the recorder and make sure there is sufficient available capacity on the disc.
Press Rec Mode/Speed to set the speed (SP, LP, SLP, or XP). Press DVD/VCR and set the unit to VCR mode. Confirm the mode with the indicator light on the unit. Press Dubbing and the mode should switch to DVD automatically. Select Yes (with the left/right arrows) and press Enter to start the duplication. The unit should indicate the VCR playback, dub and DVD recording are in progress. Press Stop to halt the dubbing process or it will stop when the unit reached the end of the tape or the disc is full.
The dubbing button is only on the remote control; if your original remote isn't working make sure that your replacement remote has the feature. Remotes.com often has exact or substitute remotes with the matching features. Search just by the model number not the brand.
BTW: the manual is available here: http://www.managemylife.com/mmh/owner_manuals/26967/SANSUI-DVD-VCR-Combo-L0311311?brand_name_search=sansui+VRDVD4005
I hope this helps.