Considering the circumstances, better (for you) to use the new supply and dispose of the old one.

Under normal circumstances, I'd suggest bringing the old one to a club meeting or equivalent, give it away to someone, with full disclosure: the understanding that as far as you know, it is not working correctly and needs repair. But these are not normal times that we live in, so if you feel better just recycling it, then that's the right thing to do.