On Sat, 18 Nov 2017 20:16:42 -0800, you wrote:
...
Be very careful with these things, as I'm sure you are aware, in many
switchers the primary is like an AC/DC radio, the negative or cold
side of the AC circuit is connected to the ground or negative side of
the primary supply. The primary is isolated from the secondary side
by way of the transformer. Connecting test equipment across the
primary side can be very hazardous and some times, spectacular.
The 2225 switching power supply is one of the very rare exceptions to
this and is not an off-line switching power supply. The input to the
switching power supply is isolated from the line by a 60 Hz
transformer which produces 60 volt DC with a bridge rectifier and
capacitor filter so it may be worked on safely without the precautions
needed for an off-line circuit.
David Hess