Adcom GDA-700 not working


A couple weeks ago my Adcom GDA-700 stopped playing. The unit powers up and emits a "thump" from the speakers when I change the input but will not produce any input sound. I am wondering if anyone has had experience working with these units particular or if this is a problem which is common to DACs. Any help would be much appreciated.
jahmann
The cost of just buying another one used is about the same as the cost of fixing it.
I own a GDA 700 (and a 600 too)
I own two GDA 700s and a 600 ..if you want another 700 let me know...probably be cheaper than fixing it...I only use one and have the other for back up in case it goes bad..Actually I think there are very few moving parts and should be easy to fix IF you can find somebody willing to work on it...give me a reply if you want mine