Not sure about this. I tested the transistors with my atlas DCA55 and they tested OK. However I had one rail getting as low as ~0.5VDC almost 0VDC and the other staying at 17VDC and the transistors did not do anything, they did not pull healthy 17V rail down. Still, when I take the transistors out they test OK. I'm rebuilding the PSU right now, will post some photos soon. I was thinking of ditching safety circuit all together as It does not work as promised. Think it was +17 rail failing with the negative rail staying at the full potential (-17VDC). All diodes and resistors replaced too.