It's funny... I'm reading this thread... and just today, I went to a home in response to a call from a homeowner who is having a party on Saturday and wanted his lighting 'fixed' up. When I went to the back yard, I saw a plethora of cheap, home depot 'lights', and two Portfolio transformers. The client was telling me that he's changed the bulbs on some but others that he did, still don't work.
I told him that it wouldn't be cost effective for him to pay me $25 for 15 minutes to fix a $5.00 light fixture. We discussed a basic design that I suggested to him and he seemed to like but to do in the fall.
At that point, I told him I had to go... and that he could try to jiggle the snap over the wire connectors that likely came loose which is why his lights don't work.
Moral of the story to the OP... buy a quality landscape lighting transformer from a trusted company and call it a day.