Well, regarding the Magnum ST, I haven't really learned enough to make conclusions. I did get a loaner and was able to confirm that my SIMMs were ok.
However, the loaner's MACH210 wouldn't even boot on my unit and vice versa. With the same ROMs too and same machine. So don't know what to think of that. The fact that my Magnum ST boots (It has TOS 2.06) says that my MACH210s at least work in decoding and therefore one could expect it to work in the other department which is alt-ram. Why then would that Mach210 not even boot on a known working Magnum ST? And why won't my Magnum ST boot with a MACH210 from a known working Magnum ST? So I decided that I'll shelve this project for now and pick it up some other time. I did some repairs and improvements that were necessary on the loaner unit and sent it back.
Since getting a blank PAK68/3 PCB, I've toyed with the idea of a SuperSTacy like DarkLord's. But I'd really hate to work with the original DC to DC board due to its size and performance (or lack thereof). Despite the various opinions of Pico PSU's and their place in Atari machines, I think everyone would agree that it would be justified due to space restrictions.
Problem is the LCD bias supply of -20V. I know that one could use a MAX629 (https://datasheets.maximintegrated.com/en/ds/MAX629.pdf
) in a circuit to generate that voltage but I'm afraid of high frequency noise that would affect everything and show up everywhere and also the resulting spikes from the switching.
How would one go ahead and create a suitable -20V for the Stacy LCD?