PAL Mega CD 2 - Cannot Format Internal Memory

Recently picked up a Mega CD model 2, which appeared to be working. Last week it would no longer power on, so I replaced the fuse as that's a common problem. Seemed to sort it, it powered back on. However, when trying to format the internal memory I just get a "cannot format" error message.

I've changed the battery to a new ML2032, but still no luck. Is it possible the RAM chip itself has had it and needs to be replaced? If so, what would be a suitable replacement and is it something a novice like me could do?

I did consider that the new battery needs charging in the system first, but I believe the system should still be able to format the memory even without a battery. It just wouldn't hold saves if powered off.

Any help or advice would be appreciated. I'm new to repairing consoles, and while enjoying the learning experience I also just want to throw this thing out a window!

Thanks

 

Yeah will be the ram ic chip bad84 is good person to ask what chip replacement