Problem running Jebao powerhead off Apex - not sure what's broken

[Delphinus]

That makes sense about how to measure amperage, thanks for that!

So indeed, I would probably have had to measure it in series to have noticed (although I'm not sure how I would do that without cutting cables so maybe it's for the best). I just stuck the leads to the outputs and saw "24v" so I assumed it was OK when in fact it wasn't. I guess the other option would have been to try to Frankenstein some kind of connector from the power supply direct to the powerhead and see if it would run at full bore 24v, then that would also have pointed to the adapter being the issue, although same sort of thing in that either cables are getting cut at that point or wires jammed into the plugs or alligator clips and probably shorting something out in the process. ("Well, the power supply WAS fine before all of this.....").

Anyhow thanks for the help!