Is the power cord frayed, cracked or otherwise compromised?
If it is, replace the power cord.
Is the connection on the 110 V side intact?
If not, replace that.
Otherwise, I agree with Brian. Come back in 100 years.
I recommend a simple test.
Use it. Check the case temperature periodically by putting your hand near it.
Touch only if cool enough.
If you can touch it, and leave your hand on it, there should be no problem.
If its too hot to get your hand close, then put it on a piece of concrete board used
for waterproof walls etc in bathrooms. My brother the plumber uses it all the time.
Its concrete, heat is not an issue.
Don't put anything on top, and keep the sides clear.