There's two fuses. The memory circuit is tied into some other circuit that is alway live, such as the horn, cigarette lighter, or most commonly, the interior lights.
Besides that, there are a few models of oem radio that have a 100 percent failure rate and can not be repaired except by the authorized repair centers. They need to have the microprocessor IC replaced and the software installed. This mostly affects the cd player or cassette player with three tone controls with yellow led lights. The cassette model number is 56038518. The cd player model ends in " 67".
There are dozens of different potential symptoms. Also, there is a different model that looks the same, mounts the same, and runs the same remote cd changer if you have one. The difference is it has one extra button for " scan". There are cassette versions and cd / cassette combo versions that are very high quality.