One fan fails to start. Presumably 12V but only 3.8 to 4V over both fans
at start up. Recognised problem /solution.? Assuming its like the 2500
(sm out there) then 39R/3W dropper, is 27R/2W in here. I can see it
being replaced with 10R + PTC thermistor of 15R hot . It would seem
that , when operating at power, a TO220 transistor bypasses that
resistor, proportionally.