I'm not understanding. You have your equipment back after you asked if he was happy and found out that he was not. If you do not ask to take it back then you do not get to take it back. If you are trying to please him at all costs this is what happens. It seems as though nothing happened that you did not allow. Maybe it did skip. Maybe he did not know how to isolate. Maybe you should have sold it "as-is'? Protect yourself first by clarifying the terms under which you will receive a return and how long you will allow this option.
If you offer a choice, then do not be unhappy if someone does not pick the option you prefer. Most will act in their own economic self-interest if given a choice. You made the offer right? He made his choice.
I would not leave negative feedback because it appears you volunteered for this situation to a significant degree . You could have just left him with his "as-is" purchase. I think you did a good thing! But leaving the unit was not a bad thing either. Just the deal that was made. Neverheless I would expect him to repay the cost of the ad and any shipping you paid. In other words you should have your equipment all you invested in the transaction back. If he does not, then I leave negative feedback. Then go and repost the equipment for sale and be very specific about what you will and will not do. Both buyer and seller need to understand what they are agreeing to. Exchange some e-mails on the subject. Be clear and be consistent. Make yourself happy with the transaction too.
If you offer a choice, then do not be unhappy if someone does not pick the option you prefer. Most will act in their own economic self-interest if given a choice. You made the offer right? He made his choice.
I would not leave negative feedback because it appears you volunteered for this situation to a significant degree . You could have just left him with his "as-is" purchase. I think you did a good thing! But leaving the unit was not a bad thing either. Just the deal that was made. Neverheless I would expect him to repay the cost of the ad and any shipping you paid. In other words you should have your equipment all you invested in the transaction back. If he does not, then I leave negative feedback. Then go and repost the equipment for sale and be very specific about what you will and will not do. Both buyer and seller need to understand what they are agreeing to. Exchange some e-mails on the subject. Be clear and be consistent. Make yourself happy with the transaction too.