I've literally these last 10 minutes just come in from the shed from dismantling two of these which were not working correctly (new design, first time I've tried these). From the outset, though they are called TB6600 - they certainly don't have a Toshiba TB6600 on board - instead, some surface mount QFP device with a splodge of heat-sink compound with a best-hope bonding to the heatsink. Also, the alarm alternates for every received clock signal - it's not a fault, but it's a poo design.

I actually came to this site on the offchance someone was selling some drivers, failing that I'm online to get something a bit more respectable.