I found what is a pretty simple way to upgrade these motherboards (Defender/Stargate/Joust/Robotron/Etc.), simply remove the 12V choke (bottom most coil) and the -5V choke, which is the top one of the four choke coils. Then run a jumper from the +5 choke output to the old 12V choke output. No cable changers (which can get lost/misplaced/buggered) needed - if you can build a cable changer you can easily modify the board. This removes the -5 and the +12 from the RAM and converts the original +12 to 5VDC which the 6164/6264 requires. Note that pin #9 which is A7 on the 6164/6264, when plugged into the 6116 socket has the 5V Vcc connection, which is irrelevant as A7 can be pulled high forever. John :-#)# -- How to subscribe or unsubscribe from TTL http://seven.pairlist.net/mailman/listinfo/techtoolslist _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com https://pairlist7.pair.net/mailman/listinfo/techtoolslist FTP site is: ftp://ttl.arcadetech.org/TTL/Test_Equipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/