Appliance switches back on when placed on standby mode

This is the service manual.

This is the standby control circuit.

My first guess is the relay on the lower right is stuck, or the control circuit has a malfunction and is holding the relay closed.

Q575 turns it off/on and is controlled directly by the micro. Standby/SysV6 circuitry on the micro schematic sheet may also be involved.

I just bought one of these at a thrift store and everything works on it for me. Looking for the user manual online and could only find Panasonic SC-PM17 instead of SA -PM17. It seems to be the same model. In searching for it I noticed lots of people asking how to 1. Turn off demo mode (which keeps you from turning the unit off) and 2. Set the clock.

The manual explains: You can't turn off Demo mode until you set the clock. AND, you can only set the clock with the remote. I don't have the remote and I bet a lot of other people don't either.

Hope this helps!