Ken W, give it a try as R1 is 1K in the Brown & Blue Atom modules, Ive also tried using 2 Zenner diodes 90v & 30V in series (120V) 5watt ones across C & E of a BD651. It still gives a sharp blue spark from crank upto 3000RPM on my test unit. CRO wave shows the Ign spike cliped at 120V protecting the BD651. The zenner diodes do get slightly warm, so don’t know about there long term reliability. Not sure where you guys bought your 2SD1071 transistors from but the 20 I purchased some time a go from China ive tested & all of them work fine.