From umn-cs!stolaf!ihnp4!harpo!seismo!hao!hplabs!oliveb!oliven!gnome Sun Feb  6 00:28:16 2
06

Relay-Version: version B 2.10.1 6/24/83; site umn-ucc.UUCP

Posting-Version: version B 2.10 5/3/83; site oliven.UUCP

Path: umn-ucc!umn-cs!stolaf!ihnp4!harpo!seismo!hao!hplabs!oliveb!oliven!gnome

From: gnome@oliven.UUCP (Gary Traveis)

Newsgroups: net.micro,net.games.video

Subject: Vectrex ROM to EPROM

Message-ID: <116@oliven.UUCP>

Date: Fri, 23-Mar-84 16:03:08 CST

Date-Received: Mon, 2-Apr-84 20:05:05 CST

Organization: Olivetti ATC., Cupertino, Ca

Lines: 97



(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.