Craigslist transaction went south...

...and then there's the idiots 'out there' that don't know how to operate audio gear that's more complex than a clock radio.  And even then, some clock radios' need the manual to make them work properly...

Case in point:  I've provided a 'shop stereo' with a receiver with a CD player, a parametric EQ, and a pair of 'line source' speaker arrays that can drown out the saws in the space.

Employ sez: "CD don't work."  Really?  OK, I'll check it out....

Later, walk up, switch on, punch ONE button on the EQ (which I've pointed out previously)....*foom* CD works....

Give the AH his $ back.  Find the manual (online?) and sell it again.  Some people can hurt themselves with a plastic butter knife and will sue the manufacturer of the knife for not providing a 'use manual'....

CYA is the order of the day. 

I gave him the original manual with remote and calibration mic. He was saying  that the receiver does not output steady
sound. I just hooked it up and no output. After a
while it has some sound output, not a little
white later there is again none and I am unable
to get anything out. I don't know what that means.

Looks like we need Judge Judy.

Actually, I think this transaction falls into the same scenario as buying a used car. Sold "as is" with no warranty, unless you told him you were providing a warranty. As long as you knew it was working properly, you can't be responsible for what he may have done, possibly causing damage.

I spoke with him or Saturday morning. I asked him to bring the receiver to my home so that we can check this out. If it’s not working,  I would be giving his money back. So far he has not contacted me.

Do you think I need to contact him now?

Sit tight.  Unless I miss my guess, no one is suing anybody for a $120.  
If anything, possibly small claims court.  

If you don't need the drama, give the buyer his money back and be done with it ... principal notwithstanding.  

It can't be worth it at this point.  

Rich