Landscape Transformer - Wrong Replacement!

[Wolf865]

Father-in-Laws old landscape transformer went out so went to Home Depot to get a new one to install that had a countdown timer once the photocell turned it on in the evenings. What HD send me home with was an Intermec Mechanical Timer. Long story short, hooked up a 120V timer on a 12V system and turned it on! The wires that hooked onto the box looked more like 120v type wires so I didn't think much about it possibly being low voltage. After realizing it was 12V went back and found they actually carried low voltage systems.! Something the "electrician" obviously didn't even know about until I found them in a different area than he took me to! Hooked in the 12V system but the lights still won't come on. Checked a couple of the halogen bulbs and they hadn't blow. Where do I even start trying to troubleshoot this to get them back on for him? Got any good advice or links I can go to? Thx in advance for any help. R