Here's where to download the manual for your box: http://tv.manualsonline.com/manuals/mfg/...
It seems you're not alone with this failing product. Here's a forum on it: http://www.digitaltvconverterbox.com/APE...
I cannot find anything on repairing it. But I've found a lot of reviews.
I don't think I've seen worse reviews since the Edsel came out