"powered up"

[DaveWM]

what does that mean, I see it all the time on ebay and CL.

"powered up fine until just a few days ago" or "used to power up" or
"powers up" are all typical phases I read.

could this be:

1) operates as intended
2) some thing happens when power is applied (noises are heard, perhaps a pilot light comes on.
3) vacuum tubes are seen to "light up"
4) raster is observed
5) white noise is heard

It just makes me laugh when I hear that somethings "powers up"