gnome@oliven.UUCP (Gary Traveis) (03/24/84)
(sacrificial line)
The following is a first stab at documenting Vectrex
hacks that have been implemented. This is mainly for
encouraging the interchange of ideas and/or programs
for a unique and yet endangered species - the Vectrex.
*******************************************************
Ok, so you want to run EPROM resident stuff on the
Vectrex! First, lets define the EPROM.
The EPROM I have been using in these tests have been
Intel 2732-2 4K x8 MOS EPROMs. Anything slower and
there may be problems.
1) Open the cartridge by taking the single screw out
of the bottom. Then, carefully unsnap the top and bottom
halves of the cartridge case.
2) You now have a little green and gold printed circuit board
with a 24 pin (Sharp or GI) ROM mounted on it.
You now have two routes possible. You can try to remove the
chip from the board unharmed (not really too bad with a good
solder-sucker tool) or simply cut the little guy out with a
sharp pair of diagonal cutters. I removed the chip, the leads
of the chip were formed such that they didn't really retain
too much solder. Ie: didn't cause any problems when removing
the chip from the holes.
3) Remove the chip. Remember that the PC board is the more
important part here.
You will notice that all but two of the traces on the
component side hook up sequentially to the edge connector
pads (gold). The order of pins 10 and 16 (remember, the
component side of the edge connector has all even #s!) seem
to be reversed.
The reason for this is because GCE (the Vectrex manufacturer)
initially designed the PC board to accept a chip with an
Intel 2732 pinout. Later, they swapped 10 and 16 (to make
them out of order) to acomodate a different pinout for Sharp
and/or GI mask-programmable ROMS.
4) So, in order to make it cozy for a 2732 again, one must
re-reverse the wiring! The way it should look, when you
finish, is -
Edge pad # 24pin EPROM pin #
-----------------------------------------
10........................21
16........................18
If you are clever, you can cut the trace, peel it
back with an exacto knife and, where the trace goes
past the correct pin, scrape the coating off the copper
conductor and solder it to the pad where the EPROM
socket will be soldered in.
The best socket to put on it is either a ZIF (Zero
Insertion Force) socket (by Textool) or a barrel-pin
socket (from Augat). Remember, a cheap chip socket
will be a real pain to replace later!
5) Solder the socket onto the pad where the ROM used
to sit. Be careful to orient it properly (socket
pin 1 to pad 1) and not to have solder bridges between
pins. You may have to bend the socket pins to get them
to sit well on the printed circuit pads.
Now, if you have no EPROM to test it with, there is
a quick procedure that will not only test your board,
but also make your old game ROM usable!
Get an extra Augat socket and mount the ROM in it
after lifting up pins 21 and 18 of the ROM chip.
Next, (tricky) wire pin 21 of the rom to pin 18 of the
socket and visa-versa.
Now your old ROM has the same pinout as a 2732! Yeow!
Plug your Augat/ROM into the socket on the board and
plug the whole assembly into the Vectrex.
Be sure to plug it in COMPONENT SIDE UP!!!
Pin one of the ROM/socket should be facing you (when
looking at the front of the Vectrex.
Now you are ready to pop in EPROMs from new and exotic
lands.