If the connections are only to the video board, then the "magic switch" is
simply a way of adjusting the "height" of the display. In one position, the
video is full height, with the standard Lisa rectangular pixels. In the other
position, the video is vertically squashed to produce square pixels. Its
pretty low-tech. The device probably has adjustable resistors somewhere on a
small circuit board in order to tweak the display for each position of the
switch. If you pull it all off, you have just the standard Lisa (full height)
display.
I think that it would be pretty straight forward to homebrew one of them.
The real Apple-supplied modification was more involved and produced a full
height, square pixel display. It included a transformer which modified the
screen height, a new video rom (which controlled generation of video sync
signals and the Lisa serial #), and new boot roms.
John
jlewczyk_at_his.com
-----Original Message-----
From: owner-classiccmp_at_classiccmp.org
[mailto:owner-classiccmp_at_classiccmp.org]On Behalf Of Marion Bates
Sent: Saturday, November 04, 2000 2:52 PM
To: classiccmp_at_classiccmp.org
Subject: Lisa WEIRD!
Okay, so after my post I went and fiddled some more and lo and behold, after a
few more power cycles it booted perfectly from the hard disk. It's running
MacWorks Plus some version or other with Mac System 6.0.3. The hard disk sounds
like it's full of sand (yikes) but otherwise it seems to be fine. :)
This is where it gets bizarre. I took the top lid off to get at the video
adjustment pots and managed to eliminate the vertical jumping etc. so the
screen is pretty much back to normal operation. But inside, on that same board
just below those adjustments, I saw two or three sets of jumper wires, the kind
with the little spring-loaded L-clip at the end. One end of one of them is
clipped to R1 right near the top of the board, and I can't see where the other
end is without really gutting the machine, which I'm not ready to do just yet.
Another jumper has one end connected to a leg of R21 and then it disappears
inside. It also looks like there's a small alligator clip connected to a heat
sink and leading off somewhere else.
So it looks like someone went in there and jumped some connections, then closed
it all back up and left it that way. I'm afraid to touch them. Maybe this is
related to the mystery switch (see my earlier post). Strange... ? Somebody
hotwired this Lisa?
-- MB
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Received on Sat Nov 04 2000 - 18:46:41 GMT