No, smk, I have not. And I had no plans to do so. I have neither the tools nor experience to get into modifying the internal components. If it comes down to that, I'd rather sell it to a hobbiest, or to an rv'er who needs a decent high amp converter to supply power to their rig's 12v system.
Personally, I believe the 12v distribution system and the battery charging system should be independent of one another, if for no other reason than not throwing 14++ volts at the various 12v fixtures during charging. And in the case where the batts are a long way from the 12v panel, it makes more sense to add a charger to the mix, than upgrading all the wiring in between.
But yes, for someone with the know how and equipment, it could very well be an easy fix. And I've already ordered a pm3-75, which I plan to modify with a simple turn of a screw, so this thing has become more of an educational process than an absolute necessity. But if I do figure out an easy fix, I will keep the unit as a back up, and apply what I have learned to getting other out-of-control chargers back in line.
