Allrighty then, so I soldered in the new chips - pulled the wires from A9 to MAD9 via 68R
Very nervously powering on - and it works!
Well - somewhat at least
It only seems to see 2Meg, or actually it appears to see 4Meg but only use 2Meg according to sysinfo...
"Total ST-RAM 4096" "Free ST-RAM 1801"
(here I had TOS 2.06 software loaded to see if it differed from original tos so it's a bit less)
I don't know why only 2meg is available booting from a clean floppy, electrically every dram pin connection is fine...
I also upgraded from TOS 1.02SE to 1.04SE, but all eproms I had was 27c512 instead of 27c256 so I had to cut the extra address pin (pin 1) and tie it to gnd.
Took some digging to find in which order to put the U2-U7 proms on my motherboard which has the proms labeled U48-U67 but it worked out in the end...
And I recapped the PSU (I read about those nasty DMA errors bad psu caps can make).
So it's been a productive day
Next up is trying to fit the PC floppy inside the chassis, and possibly trying to find some sort of flash/hdd solution.
Thank you so much for your help, really appreciate it!
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