chassis' get HOT usually only during fault conditions (rarely is it done purposesly, like "float the scope" situations). faults like a wire breaking lose and touching the chassis, or AC wires in reverse can make the chassis go HOT.
to check, use a volt meter and touch the chassis, the other pin of the volt meter insert into the GROUND pin of a receptical, or touch the cold water pipe of a house. chassis should read 0V, or close to 0V. anything over 1.5V is probably bad.
Mr.Cool
Added after 2 minutes:
it is helpful if you know if the chassis is HOT because of a DC connection touching the case, or an AC wire. keep in mind that if your meter is on DC and you are measuring your AC hot chassis, your meter will read zero and you will be fooled!!
best just select DC on your meter measure & check for zero volts. then switch meter to AC and check for zero volts.