I use two QT-1s in my system and they work great. I can send you a pdf of the manual if you don't have one. I admit it can be a bit confusing until you figure it out. The patchbay on the front confuses many people but you don't have to use that at all if you only need 4 sources (5 if you count the additional decoder loop).
As test, on the back connect a source to Recorder Inputs #1, connect your output to your amp via the To Tape Monitor Input. On the front set the #1 Record switch to the left, set the #1 Play switch to the right and the Monitor switch to Play. (Not sure if it makes a difference for this test, but put both of the Aux Decoder switches up in the Off position. Also put both switches in the Mix section in the up position.) Now see if it passes a signal.
As test, on the back connect a source to Recorder Inputs #1, connect your output to your amp via the To Tape Monitor Input. On the front set the #1 Record switch to the left, set the #1 Play switch to the right and the Monitor switch to Play. (Not sure if it makes a difference for this test, but put both of the Aux Decoder switches up in the Off position. Also put both switches in the Mix section in the up position.) Now see if it passes a signal.