In this historic cost-saving design, the power supply lacks an isolation transformer, tying one side of the AC line directly to the metal chassis. Depending on how the plug is inserted into the wall, the entire exposed metal frame can carry full mains voltage relative to earth ground. Touching the chassis and a grounded object simultaneously provides a direct path for lethal current.
Heard on the job
Don't clip your ground lead to that radio without an isolation transformer because it's a hot chassis and you'll blow up the scope.
Insider tip
Always use an external isolation transformer when servicing hot chassis equipment to protect yourself and your test gear.