My Yamaha R3 receiver loses it's stored AM/FM channels when power switch is off for
more than a few minutes.
The power switch directly switches all mains power in the unit, i.e., there is no
standby supply to any circuits.
I cannot see any internal battery.
I therefore think the problem is a faulty memory device LC7030 or a faulty
capacitor.

Do they use caps (electro) for memory retention?

The user manual states that the Receiver may lose it's stored channels when
*unplugged* for a long time. As far as I can tell being switched off is equivalent
to being unplugged.

I would like to understand the circuit around this LC7030 device which appears to be
where the channels get stored. Does anyone have a R3 circuit diagram or datasheet
for Sanyo LC7030.

Thanks for any advice.