A3010 not booting - memory problem

[Nutter]

I have an A3010 with both:

RAM control line failure and
CMOS RAM checksum error

There was a very minor battery leak in this machine but only R60 seems to have been affected (although it still seems to be good). I'm assuming the CMOS fault will clear when I can get the machine to boot with DELETE held. However the RAM fault seems to be playing a part here. There is no physical damage around the RAM (and plug in expansion zip chips). However IC22 heats up quickly and runs very hot compared to IC21. I was going to attempt replacing IC22 but wanted to check which equivalents can be used.

I have seen pictures of both NEC424260 (uPD424260 ? ) and HM514260AJ8. Are there any others that would do the job?

While poking around the RAM modules with the 'scope I found there was no activity on IC25 pin2 (dbe pin 40 ARM250). TBH I'm not sure what should be showing at this point but permanent 0V doesn't seem right (or maybe I'm wrong?)

Any pointers appreciated.