NAD Station Preset Memory
New to Hifiengine, but have enjoying Vinylengine for a few weeks. I have an NAD 7155 receiver in pretty good condition but the station presets only last in memory for a few hours. I downloaded the manual and service manual from the site, but all it says it they should last a month or so with power off. Did this vintage period use a backup battery or a capacitor to keep the memory live. Is it repaceable? Keeping the unit on 24/day seems wastful. Thanks in advance.