I find it relatively easy to probe the voltages on an XL/XE power supply, as long as the probes aren't too large in diameter. With my method it is important to verify that the outer metal shield isn't connected to ground, or if it is make certain that it is the ground pins that are being connected to the shield when probing.   I hold the DIN plug and a probe with a connection between the outside of 2 pins on 1 side and the metal shield,(black circle in image) a little pressure between the 2 p