The Great And Powerful Primary
As usual when messing around the primary side, be aware that most circuits there are referenced to the negative end of the input filter capacitor(s), which means up to about -170V might be present on 120V input. An additional detail to keep in mind is that this unit has active power factor correction and when the main outputs are active, the full APFC boost voltage of about 350V will be present. Because my probes and oscilloscope inputs are only rated for 300V to ground, I won't be able to probe the primary side while the main outputs and APFC are active.