On 7/15/22 17:49, David Anderson wrote:
The A&J Microdrive was made by a company spun off from Exatron, who made the
“stringy floppy” cassettes. The Wafadrive is the same mechanism, but made by BSR,
who had a stake in Exatron, I think. It’s been a while.
Anyway, the drives and cassettes are kind of hard to come by. They show up on
the bay once in a while.
David
Yeah, I found a little more info, A&J spun off from Exatron, and they
made a drive with the same microdrive name for the Sinclair that did
still use the same stringy floppy drive & tape, but then BSR made a
slightly different drive later and that's what this and the Rotronics
Wafadrive has.
It's this:
https://ftp.whtech.com/club100/doc/p100-8604.pdf
pg 33
I also found an old mail list post where someone described the same
drive I have right down to the peculiar battery wiring inside, although
it's not as peculiar as they thought, but at first glance it looks like
what they said. It's a 4xAA holder with 2 cells that don't look
connected but they are. It's just an odd 2->3->4->1 arrangement where
the link from 4's pos over to 1's neg is hidden. The arrangement makes
it so that the + and - for the pack come out together at one corner
instead of at opposite ends of the pack. And there is a tap at the +1.5v
point, but that tap is connected to a via labelled GND, and has
continuity with another point marked GND, but neither of those are
continuous with what looks like the ground pour, which the overall pack
neg is connected to. So the pack is not producing +1.5 and +6.0, it's
producing -1.5 and +4.5? Ahh, corroboration, I found a pin labelled VEE
which is on that "ground pour", and it has continuity with the pack
negative pin. So it's a VEE pour at -1.5v after all. (I'm only looking
at this by eye and testing continuity, not powered up.)
That tap is super annoying. I WAS going to rig up some battery blanks or
just alligator clips or J-grabbers or something and run a wire out
through a gap in the back cover that's already there at the serial cable
grommet, so that I would never actually put batteries inside it and
close it up like I found it. But now that's out the window. Well, since
I may never find a tape for it anyway, I guess I'm safe.
Another odd thing about that tap is it's just thin wrapping wire. Even
though it's going to "GND", still the bulk of the current (one would
hope) must be going via the packs normal main pins, so, something, the
motor I guess at least, must be running on the full 6v differential and
drawing the most current that way, even though there is a gnd reference
at -1.5 gnd +4.5. So, even if I wanted to go so far as to rig up 2
little buck converters, I have to worry about the end to end 6v
differential too not just producing two outputs just wired so one ends
up being negative? I guess it shouldn't really change anything, maybe
it's no real worry.
--
bkw
