Ptss,
I was given an original "white toaster" Z Stabilizer unit many years back.
The power switch never lighted up when turned to the on position, the unit itself was dead silent and either the audio system being auditioned was not sensitive enough for me to hear improvement, or the unit just never turned itself on.
Would there have been a way to know for sure if this unit was mechanically or electrically broken rather than just ineffective?
It has been in storage, too good looking to discard, waiting to be awakened by some knowledgable audiophile.