Sylvania LC427SSX Service Manual page 52

Jack Power CBA Top View
Because a hot chassis ground is present in the power
supply circuit, an isolation transformer must be used.
Also, in order to have the ability to increase the input
slowly,when troubleshooting this type power supply
circuit, a variable isolation transformer is required.
NOTE:
The voltage for parts in hot circuit is measured using
hot GND as a common terminal.
10-16 BA94H0F01011-A