My first was a SLC 150 in a mk.1 machine and a 5/02 in mk.2 of the same machine. I upgraded the 5/02 to an 03, the PLC was ok but the DTAM was dead so went for a PV micro 300. The 150's were replaced with a cheap controller as it was my first plc project. I didn't connect to the 150 and pull out the program, instead re-wrote it from scratch by studying the user manual and watching the machine. Relatively new stuff compared to the others in this thread, but then I was born in the same year the 1745-800A self-teach manual was published.