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• 3M calls their 2123 insulating resin "reenterable" so the stuff can certainly be removed and the boards can look quite... intimidating when they first come out of the box but with a little patience and a little work they clean up well enough to allow repairs and/or changes. So, all P5 boards built since 2004 are potential candidates for conversion to digital ZDL switchers and/or ZDL simple flowmeters. The list of potential candidates would normally include boards built back in the 90s, unfortunately however, the potting compound used up to the end of 2003 does not allow those boards to be reworkable. So "See you later, alligator" for those so-called PDLs...
• Close reexamination of multiple old boards revealed the ultimate truth in the end: The "crazy greek", and "crazy" wasn't the usual adjective but that's another story, who wanted to put expensive electronics in a $30 plastic box, ha ha that's so funny, and have the entire assembly sit at the bottom of lake Erie for decades, wasn't all that crazy after all. But you know Jack, after three years of no switching failures, I couldn't help but notice, nobody is laughing anymore...
• Close reexamination of multiple old boards also revealed something unexpected, something completely forgotten: Because I designed these boards I know that from the hardware point of view a P5 was a P4 with a faster crystal. The recent switching success with the P5 switchers was accomplished with the same boards the dismal failure known as the "trustco fiasco" was done with back in 1998. It didn't have to happen, the hardware was already perfected in '98! History v2.0, 1998-1999.
• Further, the switching circuitry in the PDL3 (1997), PDL4 (1998), CDi99/PDL5 (1999), CDi3/P7 (2011), and the upcoming CDi4, the switching circuitry on all five boards is identical, these boards were designed to drive two latching solenoids since at least the PDL3 in '97!

The NTRM, "Nothing To Repair Man", November 18th, 2017