actual Apple II number 1.299 on left, my
replica on right
(rev 0 images provided by Geoff Harrison - www.solivant.com)
here for close-up comparisons of my replica and the original rev 0
Background on the Apple II Rev 0
The first 6000 or so Apple II's sold,
what is called a revision 0 motherboard. A number of Apple II
motherboards were also sold at the same time without case, keyboard or
power supply. Most of these bare board systems were revision
One of these early machines was my personal Apple II.
some point, when the machine was on loan to a family member's business,
the original rev 0 board failed. It was repaired via
replacing the motherboard with a rev
3 board. Over the last few years, I've been working to
the machine to original condition. In the process, I've spent
long time looking for an appropriate Rev 0
With only 6000 made, rev 0
boards are scare
and very expensive when you do see them on eBay. I would hate
to buy a complete Apple II with original Rev 0 board, only
to separate the board from it's matching case, keyboard and power
supply. I needed to find either a bare board or a mismatched
machine. After a couple of years of hunting around for a
rev 0 board, I realized that it would be quite a while before I would
find what I was looking for. I decided that I
would try to build a replica of a Rev 0
motherboard for my old machine. It seemed like it would be a
and challenging project. This project also would be a good
put my machine back into a state closer to original condition.
turned out that I was right on all counts.
What Makes a Rev 0 Board
were enhanced in several minor and a couple slightly more
significant ways. Many of these differences are documented on
PCB layout page. The most significant two changes to later
boards was the addition of a power-on reset circuit and the addition of
two more colors to HI-RES graphics mode. In the end, the
reset change was not significant, because all Disk II controllers also
included a power-on reset circuit and most all Apple II's eventually
were equipped with floppy disk drives with this reset function.
Programs that used the additional two colors of the later rev boards
are almost always perfectly usable with the rev 0 board. The
result is that rev 0 boards are almost as capable as all later revision
Apple II and Apple II plus boards.
Identify an Apple II Rev 0
Motherboard at a Glance
for the large prototyping area from A-11 to A-14 that could be used for
add-on circuits. This area is vastly reduced in later rev
boards. A significant portion of it was used to
make the changes to add the reset and the additional colors in these
transistor near location F-13. A
was added to rev 1 and later boards that included a transistor at this
location. This transistor was supposed to suppress the color
output during text only mode. This change didn't completely
the color burst signal and depending upon the monitor or TV that was
being used, the color still might be displayed in text only mode, even
on later rev boards. This transistor can usually be detected
on relatively low resolution images of later rev motherboards.
1977 printed under the Apple Computer
Inc. logo. This is usually hard to detect in most web images.
Build Your Own
Rev 0 Replica
Saga of the Rev 0 Replica Project
Apple II Rev 0 Evolution
Apple made it's computers in batches - they made some minor tweaks to the rev 0 as new batches were made.
Rev 0 Hardware
modifications bring a rev 0 board closer to later rev hardware
standards. The instructions for these modifications were
widely distributed back in the old days. The Apple II was
designed to be a platform for hobbyist, so it wasn't unusual for
owners to actually apply these changes
- Color Killer
(page 6 of Apple's Contact Newsletter - June, 1979)
- Adding Colors
- Byte Magazine Article from
June 1979 - found at reactive micro web site - link to article (error in
schematic - pin 1 of 74ls74 is missing connection to soft-5 - a2-8)
- Woz Wonderbook, pages
37-41 - found at digibarn.com web site - link to document (note that
schematics in this copy are almost illegible)
- My translation of
illegible Wonderbook schematics. Also Pin 7 of 74LS02 goes to GND and Pin 14 goes to +5v.
- to avoid damaging or altering your
motherboard, the two new chips can be glued upside down on existing
chips with hot melt glue rather than be soldered in proto-area.
Put the 74ls74 upside down on A-9 and the 74ls02
upside down on B11. Keep in mind that upside down chips have pins
on opposite sides of the chip compared to right side up chips.
- Adding Hsync Serrations fo Vsync signal,
described in the book, "Understanding the Apple II" by Jim Sather.
- Woz Wonderbook, page 42 -
found at digibarn.com
web site - link to document (note that this
page is almost illegible)
- My translation
of illegible Wonderbook schematics
later rev sync circuitry. The change documented in the Wonderbook
turns out to be different than what was added to later rev boards.
If you have trouble with distortion at the top of your screen,
here is a mod that gets you later rev Hsync and Vsync signalling on a
rev 0 board. This mod is something
I came up after a replica builder encountered this issue. I have
made the mod on one of my boards and tested it. Also mentioned is
a much simpler hack that also helps stabilize the picture.
My Apple II restoration pages
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