DRAM 128K system has stopped working

[CheshireNoir]

Thanks Ernest.
I don't think BN56 works with non Premium systems? I can try it. There's quite a few versions of the BN54 ROM in the repository and I'm not sure what the difference is between them. Do I want the bn5443 ROM or a different ROM?
The EPROMs I'm using are TMS 2764JL-30 ROMs salvaged from upgrades to the PC85 coreboard. I think they're TTL not CMOS? (Hard to find a data sheet)
While there's a spot for a resistor network (RN1) over near X1, there's only a single resistor on it. There are no other resistors in the area. Is there documentation on the resistor mod? ECN 2-090487 would seem the appropriate mod?

Cheers!

Chesh