Dead power head/smoky smell

[drknudsenx2]

Did my first water change today on my 75 gallon tank (about 20 gallons), and went to run some errands. Came back and smelled a smoky smell, like electrical burn smell or the smell when you drill out a screw. I think one of the power heads died, as I received a small shock when I took it out, and when plugged in is not functioning. What concerns should I have for my tank? It is currently cycling, so no live stock. What may have caused this? Anything to do with the water change?

 

[drknudsenx2]

EDIT: both power heads suddenly dead- unsure when they were both working, but definitely both worked. Any idea what happened?

 

[BarSnackz]

When you did your water change: did you turn them off to ensure that if the water level dropped below them, they wouldn't run dry?

 

[drknudsenx2]

When you did your water change: did you turn them off to ensure that if the water level dropped below them, they wouldn't run dry?

I had them off, because they are on the same surge protector as my pump. I actually pulled the water from the sump, and then replaced the water back into the sump. I can’t say for certain, but I’m pretty sure the water level in the tank barely changed, and likely not below where I had the power heads placed.