Ah good so the SRAM hookup for /CE etc at least works enough to boot the machine - getting there. 
Update: boots but nothing loads. Obviously adjustments required. If you can advise RT, it would be appreciated. 
That's because ROM address lines 14 & 15 aren't MA14 / MA15 (or even Z80 A14/A15). So 16K blocks from the SRAM are addressed in a weird manner (I don't feel like checking, but you've probably got a 16 or 32K RAM machine now).
You need to use MA14 / MA15 from the S1985. Schematic says they're not used anywhere, so there's no way to get around soldering to the S1985 directly - be careful! (I pull wires from an 80-wire IDE cable for jobs like this). Also MA16 / MA17 and MA18, it'll get crowded in a spot there. 
Btw. HB-F1XD schematic also shows MA14-MA16 that go from IC15 (MB64H444) to ROM. Forget those - you need the same-named signals from S1985 only.
512K may not work right away, this is because MA18 doubles as a keyboard signal (KBDIR). Not used in this machine, but it might be set to that function on reset (see beginning of "3. Selection of functions" for details).
Thanks for that datasheet sd, very handy 
Are pins MA16, 17, 18 used anywhere RT so that I don't need to solder directly? 
I don't trust myself with too much soldering in such a small area 
Now soldered, says 256kb RAM at bootup
Update: testram says slot 3.3 064k size
syntax error in 220
Bootup still says 256k.
Games load but corrupt screens
way over my head 
How do I do this? Is there a way I can set it to default to MA18 function and not Key/DIR?
