On 30 Dec 2009 at 2:29, Adam Sampson wrote:
Which is perfectly reasonable -- but you can get the
same effect by
putting the shared PSU in the computer. The Amstrad PCW 8256/8512 used
that approach: monitor with integrated CP/M machine, simple dot matrix
printer powered from it, and a separate keyboard. This meant that you
didn't need to connect the printer if you weren't going to use it, and
third-party printer upgrades were fairly common.
The Joyce PSU is something like the early Mac ones--basically run off
the flyback transformer for the CRT. Very, very little excess
capacity--indeed, if you're printing, the display goes a bit wonky.
It's not what I'd call a desirable setup. And Cthulhu help you if
you accidentally overload or short a power supply output--there are a
bunch of circuit protectors in TO-92 packages soldered onto the video
board. I'd never seen one on this side of the Pond before, and it
took awhile before I tumbled to what they were. I just replaced the
blown ones with picofuses.
--Chuck