Hello!
I picked up my first lab power supply after years of not having anything. It is a Siglent SPD3303X-E.
This is a linear power supply with two independent outputs that can be connected in series or parallel. As far as I know, the outputs should be "floating".
I turned the power supply off but I still had it plugged in to the wall. I started measuring the spacing between the banana terminals with a caliper. I measured them by the base, where some metal is exposed.
When I bridged the positive output of channel 1 with the green earth connector and I saw a spark. It was not big, and it did not spark again while I kept measuring things. If I'd have to guess, I shorted a capacitor.
As far as I can see, nothing is broken.
I tried measuring the voltage between the earth connector and the positive output terminal of channel one but it's only a few millivolts.
So, to the question:
Is this normal?
The only thing that I can think of is that there is a capacitor between earth and the output terminals (I've seen this in some power supply designs) and when I touched the output connectors with my caliper, I shorted that capacitor.