The trim pots on my Melzi do not appear to have a stop so I can keep turning them counterclockwise. On my board, turning the pots too far counterclockwise makes REF (top of the pot or the pot pin closest to the stepper motor driver) become an open with respect to ground.
So, I needed to monitor the resistance of REF to ground while adjusting the pot to reach the low starting resistance needed for first power up.
Afterwards, I applied power and adjusted the pot to acheive the 0.4 volts on REF.
