Unitron EPROM Writer UPDATE

["Mark Cummings" <NOTfigjams@primus.com.au>]

Tim,

I have been working on those scans to draw out some kind of circuit drawing.
While the back is pretty easy to follow, I'm afraid it's impossible to
follow the tracks on the component side without actually having the board in
hand.

Unfortunately while that close up scan does make it easier to read the IC's,
it's still pretty hopeless trying to see where those tracks go in the
shadows or under chips.

So far I don't have enough of the circuit to come to any conclusion, but if
you can trace (follow) some of the tracks on the component side that may
help. I assume you know how the chips pins are numbered. If you can remove
the chips temporarily that may help, just keep a note of where they go and
which way. Also that ZIF might get in the way, my AP-64e EPROM programmer
has a socketed ZIF so I can pull it out, the Unitron one appears to be
soldered onto the board.

this is what I need to fill in some of the gaps:
where do the following tracks go to (if they exist) on each of the following
?
(BTW if the track goes to a passive component, like a resistor or capacitor,
forget that and keep following it to a chip leg if applicable). Some may go
to a few places.

1. Socket 08 pin 1, 5, 6 & 12
2. Socket 16 pin 3, 11 & 12
3. Socket 32 pin 2 & 3
4. Socket 64 pin 1, 3 & 6
5. ZIF Socket pin 2, 26, 27 & 28
6. 7406 pin 1, 3 & 7

Although I can't see these can you confirm the following:

(A9) ZIF pin 24 - 4040 pin 14
(A8) ZIF pin 25 - 4040 pin 12
(A7) ZIF pin 3 - 4040 pin 13
(A6) ZIF pin 4 - 4040 pin 4
(A5) ZIF pin 5 - 4040 pin 2
(A4) ZIF pin 6 - 4040 pin 3
(A3) ZIF pin 7 - 4040 pin 5
(A2) ZIF pin 8 - 4040 pin 6
(A1) ZIF pin 9 - 4040 pin 7
(A0) ZIF pin 10 - 4040 pin 9

I'm still working on the theory that the header will be wired as:
1-14
2-13
3-12
4-11
5-10
6-9
7-8 (although I'm not sure if this last connection is used)

The chips you need were:
7406 - quad NAND gate Open Collector (don't use any other type or the smoke
will get out)
74LS74 - dual D Flip Flop +ve edge triggered.

I am not sure why +12V is supplied from the Apples bus pin 25, unless the
programmer also programs 12V EPROMs. Most older EPROMs were 21-24V. This
might complicate the issue, although I'm hoping if you can supply some or
all of the above answers it might become clear.

BTW: Congratulations on getting the GS networked to your Win2K PC, I bet
that has taken your fun to new heights, and this little EPROM project will
probably take a back seat for a bit.

Mark