It's probably the adapter. Good that you caught it !
I'd suggest taking it out of service immediately until you can replace the power adapter. No sense risking the Slingbox (or a fire).
SlingMedia sells a replacement:
If you decide to pick one up locally, here's a snip from the Classic's User Guide:
I'm not sure about the polarity though, which is very important. Other Slingbox models use tip-positive polarity but that's no guarantee this one does. If you find your own power supply and get the polarity backwards, you'll probably destroy your Slingbox. For this reason, I'd suggest ordering a replacement from Sling unless you find reliable information on the correct polarity somewhere.
Update: It didn't occur to me to turn my Classic upside down and take a look (duh). Here's what I found:
Apparently, the polarity is Tip-Positive. (Click to enlarge)
Good luck !
Message was edited by: ArizonaSackbut
I enclose a picture of my adapter, the hot and tried to find a good way to contact the manufacturer as this is a guarantee, but in the meantime, I have reported it to The Electrical Safety Board in Europe, put into this issue yesterday on the forum to see if others had errors in their information and were removed. Sepa pictures and judge for themselves, have never descend past ways and it is CE marked
Interested to learn if you found a replacement?
I have recebtly had broadband problems - low speed, disconnects etc.
Even after a visit by "BT" the problems remained.
Eventually, using an AM radio, I discovered that the Slingbox PSU (same as your picture) was not only "buzzing" but also radiating lots of interference.
Unplugged it and bingo broadband OK!
So now need to find a new PSU..
A few weeks ago I smelled something like burnt plastic in my basement but I couldn't find the source. Just this morning I was doing some work on my rack and heard a buzzing. Traced it back to the slingbox classic power supply. It was very hot to the touch, I'd say around 150 degrees and had oozed out some nasty smelling sticky stuff. The rack is on UPS and also has an additional power strip behind it. First time I've had a powersupply like this fail this way. Very much a hazard, if I didn't catch it, who knows what would have happened down the road. I encourage everyone to check their power supplies.