I had the same situation happen to me but I was the buyer. If I had to do it all over again, I would have promptly shipped the unit back to the seller for a refund and allow the seller to arrange for the repairs to be made, as per Audiogon buyer/seller recommendations.
In my case, I bought a DAC from someone who is no longer here on Audiogon. When I received the unit, I connected it to my system and found that one channel was dead. I immediately contacted the seller who was surprised to here of the dead channel which was later found not to be from shipping damage. The seller then asked that I have the DAC repaired by the DAC's manufacturer and send him the bill. To make a long story short, I did as he asked, and the bill, which shocked the heck out of me, was over $800.00, but the seller decided the he would only pay me $500.00 for the repair. All and all, I guess that I'm lucky to received that much, since seller could have told me to take a hike.
Again, if you read the Audiogon recommendations, somewhere in there it is stated that if equipment is receive by the buyer in a condition that is not as advertised (i.e.: doa, dead channel, etc.), that piece should be promptly shipped back to the sell for a refund. At that point, the seller takes control of the situation. Which I think would be a good thing in your case.
In my case, I bought a DAC from someone who is no longer here on Audiogon. When I received the unit, I connected it to my system and found that one channel was dead. I immediately contacted the seller who was surprised to here of the dead channel which was later found not to be from shipping damage. The seller then asked that I have the DAC repaired by the DAC's manufacturer and send him the bill. To make a long story short, I did as he asked, and the bill, which shocked the heck out of me, was over $800.00, but the seller decided the he would only pay me $500.00 for the repair. All and all, I guess that I'm lucky to received that much, since seller could have told me to take a hike.
Again, if you read the Audiogon recommendations, somewhere in there it is stated that if equipment is receive by the buyer in a condition that is not as advertised (i.e.: doa, dead channel, etc.), that piece should be promptly shipped back to the sell for a refund. At that point, the seller takes control of the situation. Which I think would be a good thing in your case.