Thanks you very much for this "hard to find" service manual.
Will help a lot in repairing this receiver.
Text excerpt from page 52 (click to view)
Inverter Power CBA Top View
NOTE: The voltage for parts in hot circuit is measured using hot GND as a common terminal.
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.