Using 4164 DRAM with Williams Video Game CPUs
This modification was originally developed by Mike Ranger to allow use of unmodified 4164 DRAMs on Williams video games from an earlier idea by Clay Cowgill on modifying an individual 4164 DRAM to replace a single 4116 DRAM. I can personally recommend his modification and I use it on all my Williams games. I have never had a single 4164 fail to date ... but I have a jar containing 2000+ failed 4116's!
Many thanks to Clay and Mike for their efforts.
Below are some pictures of MY 4164 adaptor which is slightly different in construction to Mikes but the wiring is the same:
Williams 4164 Power Adaptor Front
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Williams 4164 Power Adaptor Back
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The text below is an EXACT copy of the text that Mike posted to the raster-list a few years ago describing the conversion of his Blaster, but it applies equally to Defender, Stargate, Robotron, Joust, Sinistar, Bubbles and Splat!
This hack allows us to used UN-modified 4164 RAM in place of the 4116 RAM, without modifying the board, harness or RAM (didn't I already say that?). The advantages are, 4164 RAM is plentiful, we no longer use +12 reg and -5 from the PS, eliminating those points of failure, and the RAM runs allot cooler, leading me to believe we may be easing up on the +5 requirements.
I owe Clay some kudos' on this one for showing us the similarities between 4164 RAM chips and the 4116 RAM chips in a way cool (yes I am a geek) graphical format.
I started by making an adapter for the power input to the CPU board. I did this with a 9 pin header strip, just like the one mounted on the board, and a female counterpart. I wired it up as follows:
Pin 1 nothing
Pin 2 straight through
Pin 3 straight through
Pin 4 cut off the male pin, as it is the key
Pin 5 looped (see below)
Pin 6 nothing
Pin 7 longer wire, straight through AND looped back to pin 5
pin 8 straight through
Pin 9 nothing
Heat shrink tubing on the connections to the male header.
Notes: When I say looped back, I am using the punch down style of female connector that allows you to punch down a longer wire in the middle at pin 7 and then I loop the end and punched it down into pin 5.
So, If you have read Clay's 4164 replacement hack, you will see that pin 1 of a 4164 is N/C and is -5 on a 4116, so I just left pin 9 not connected, hence -5 of the supply is not being used.
Pin 8 of a 4164 needs +5 as it's supply voltage. This is +12 on a 4116, hence I looped the +5 from the 5 volt supply to the 12 volt reg pin. Pin 9 of a 4164 is the high address line, and is +5 on a 4116, so it can be left alone, and we will only be using 1/2 of the RAM's capability.
A careful study of the schematics reveals....
+5 used all over the place -5 only used by RAM
+12 reg only used by RAM
+12 unreg used by reset circuitry
Looking at the rest of the schematic package for Blaster reveals that no other board uses +12 reg, or -5, so that part of the power supply is no longer used. +/- 12 volt unreg is used by the sound board(s), but that is generated byte he + 5 part of the PS board.
A problem in the joust schematics shows that the blitters use +12 reg, but that is just not so. +12 reg is not fed to the ROM board. The SC2's on the Blaster set show pin 15 as N/C which is the corresponding pin on the SC1's which say +12, but the harness does not supply the ROM board with that voltage.
When I originally did this hack a year ago, I ran a Robotron board for 4 hours and the 4164 RAM was still cool to the touch. A far cry from the heat generated by the 4116's in about 5 minutes!
I then removed all the 4116 RAMs from the Blaster, and I'm glad I did. I lost no fewer than 10 pins in the 24 pulls. Corrosion had got the better of these. I cleaned out any sockets that had pins stuck in them, and populated the board with 4164's (cheap chips, and plentiful). I found 4164's at a surplus store for $1cdn a tube (25).
Use this hack at your own risk! Populating the board with 4164's and applying the power without the adapter will fry all the RAMs. Having 4116's in there and using the adapter can't be to good either!
|Disclaimer: Although I have done my best to ensure that all information contained on this
page is correct, I can take no responsibility for damage to your game, its boards or yourself!