Amiga tech A1200's had a minor hack done to the bottom of the board that puts the diskchange line to pin 2 and pin 34 at the same time. Therefore, the RDY line (indicates that the motor has reached full speed) is not available at all, so some demos and trackloading games might not work (for example the ARTE demo by Sanity).
If you have access to a real Amiga diskdrive, you'll have to reverse the dickchange/RDY hack. Just remove the wire on the bottom, and use it to connect RDY to the 34-pin internal floppy connector (RDY is supposed to be on pin 34). You can take RDY from pin 1 (square pad) of the 23-pin external floppy connector. That's all to make your Amiga 1200 fully functional with *all* trackloaders.
If you don't have access to such an Amiga drive, go for a PC diskdrive and change it's select line to 'select 0'. Most PC drives don't have such a jumper any more, and they're hardwired to be 'select 1'. Either look for one that has a jumper or a switch, or swap the two lines. Again, this hack is only possible with the Amiga Technologies A1200. Others don't have the diskchange line in the right place (PC diskdrives have it at line 34), so they won't work at all.
Hope this helps,
Jens Schoenfeld