There's probably a lithium battery for backup on the board.
JR
Fred Besancon wrote:

I'm presently servicing a Marantz SR-18 for center channel distorted.
That problem
has been repaired (cold solder joints). I noticed that even though the
unit is plugged
in the AC, when turned off and then turned on again, the last settings
are lost.
The unit goes into initial default: FM at 87.5 Mhz and the volume at
minimum.
This doesn't seem normal??
Any help is appreciated........Fred


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