I received the final prototype boards on Monday, and assembled the first one using parts from the test BOM (Bill-Of-Materials) order. The purpose of doing this is to make sure the Bill-Of-Materials and the board are correctly specified, so that when I send the order to manufacturing, I can expect it to work.
It didn’t work at first, which was cause for concern, but it turned out that one of the PNP transistors was no good. Once I had replaced it, everything worked perfectly.
Once the Tempco resistors have arrived (mid-August), I will build the rest of the boards, and send them off to my test subjects.