Marantz PM66SE signature - repair/troubleshooting

I believe I may have confused you all, I assumed the source switch was also linked to the mute operation as I could not get the LED to turn on. I originally ask about a user guide as I could not see how the mute LED works following my repair. I now understand that the switch under the mute LED is only the Source switch to select direct or balance output and does not control the mute LED. I now believe that the mute LED could be possible be operated from the remote control as Medis64 suggested and not possible from the front panel controls.
 
The 'MUTE' function is only available via the remote control. All it does is remove power to the speaker & headphone relays and illuminates the 'MUTE' LED. It's not worth purchasing a remote control for that useless function.
If you want to emulate the 'MUTE' function without illuminating the LED, insert a 6.35mm jack plug into the headphone socket.
I've repurposed the 'MUTE' LED and function on this machine...
 
Usually the mute function is operated - physically - from a switch that is labelled "Mute" on the front panel.
If such is missing then the only remaining option is remote control ;)
Thanks it looks like you are correct re the remote function, still cant find a user guide to confirm this, however, I don't have a remote and I'm happy with PM-66se as is.

Thanks again
David.