Instead of resorting to a dork machine (what Poliquin affectionately refers to the pull down machine as), simply perform several eccentric-only reps. In other words, stand on a bench or jump up so that your chin is over the bar. Now, lower yourself in a slow and controlled manner. That’s a good start.
For an eccentric-only routine, perform four sets of one eccentric rep so that each negative portion lasts for 30 seconds. Once you get the hang of that, try stopping the movement on the way down. Begin with your chin above the bar, lower yourself slowly until you’re one third of the way down, and stop – hold this position for eight seconds. Drop again until you’re about halfway down and hold the position again for another eight seconds. Finally, lower yourself again until you’re almost at full extension and hold again for eight seconds (you probably can’t get the full eight seconds on this last one just yet, but set that as your goal). Sometimes I have my athletes lower themselves for 30 seconds on the last rep of each regular set. Another variation is to pause isometrically on the way up. If you’re shaking as though you’ve just been zapped by a police taser, you’re doing it right.