Ah, I was not understanding how the current limiting resistor works.  Looking at the schematic, does it give a reference voltage for the 2n3904 and that feeds back to the C2M? Doh!   Sorry, mwl168, I was being dense.  Now I understand the importance of that resistor!! Out of curiosity, how do I calculate the current limit imposed by the R11 (the current limiting resistor) in the circuit?   What limit does the existing 5R1 impose?     EDIT: Partial success!!  I changed the cur