Rev 0 Replica Bringup
Start with only one bank of memory installed and no Apple PROMs.
When you first power up, immediately feel around the board for hot
chips. If any chips are hot power down immediately and check for
solder bridges on circuits connected to that chip.
If you get no video or bad video, you are going to have to go into
troubleshooting mode, but my first guess is always something relating
to the clock generation.
you have good video, power down and install some Apple PROMs (start
with less valuable Applesoft PROMs) and power up again. Don't forget
that on a rev 0, you need to reset the system in order to get a prompt
- you can short pins 3 and 8 of the keyboard connector together to
reset, if you don't have a keyboard installed. Hopefully you will
be now in business and you can check out the rest of the Apple II, in
any order that you choose.
Here is what happened, when I brought up my very first rev 0 card.
Initially I got no video. Probing found no clocks at all.
Traced it down to wrong transistors in clock circuit. After
taking the right ones from an old rev4 board, it came to life, but no
text - video mode only. I found a bad IC. The 74166 at
location A3 had a bad output. I did another swap from the rev 4
board and now I had a text prompt, but no color. Swapped the
crystal from the rev4 and color appears.
Now I wrote a simple program that randomly plots color squares on the screen (see picture).
Tried booting DOS and it
dropped to monitor instead. After thinking about it a while,
remembered that I needed more than 16K ram to run DOS. Filled up
memory to 48k and now I could boot DOS. Booted from all the slots
Now that Disk II is attached, I load a program that utilizes high res graphics and it is working fine.
Next I checked out the paddle and switch inputs by attaching a joystick
and writing a simple basic program that prints values of paddle and
switch inputs in a loop. Everything is fine here.
I now checked annunciator outputs. I simply connected a LED to a
resistor. I connected one end to game port ground, and probed the
annunciator outputs with the other (with LEDs you have to make
sure you get the right end on ground). I toggled the outputs with
the Apple monitor.
For cassette I/O, I connected an old cassette deck and tried saving and
loading several basic programs. Keep in mind that for reading
tapes, volume of the tape deck has to be carefully adjusted. Just
to make sure everything was really good, I found an original Apple
supplied tape dating from 1978 and made sure that I could read that
one, as well.
For slot 0 functionality, I added a language card and checked to make
sure that integer BASIC would get installed and run properly when
I've check 4k memory configurations, and it also looks good.
I've completed checkout of this design and have found no errors on the PCB.
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