Replacing the NVRAM on Gottlieb System 3 game boards.|
By, William Stephens
(clicking any picture in this article will bring up an enlarged version)
The procedures outlined in this article are very dangerous for the clumsy and inept among us. If you think this applies to you then read but don't do, you might kill yourself.
When fixing a system 3 board do you sometimes get:
CONTROL BOARD ERROR|
LOW BATTERY or
BAD U3 or U6
This is usually due to a bad battery and sometimes due to a bad run of RAM chips (U3) around the release time of Shaq Attack. It could also be the Dallas Non-volatile chip controller (U6). Back when this board was designed they did not have access to modern technology like FRAM. What the designers wanted here was non-volatile RAM and this was accomplished by using an 8Kx8 CMOS RAM chip (U3) supported by a Dallas NV Chip controller (U6) and a battery (BAT1). Unfortunately with this design if there is a failure somewhere in this NVRAM circuitry, the game will not boot. Actually the game continuously tries to boot, blinking mindlessly away and getting nowhere. The dotmation display will either display the aforementioned error message or will flash weird characters and numbers. The U8 status LED may be glowing steadily looking like a GAL failure (which it's not) and the A1 status LED may be blinking erratically. No other status LEDS will activated in this condition.
Now, to the rescue, comes the FRAM revolution. Flash RAM to the uninitiated is non-volatile RAM which can hold information while being flexible as RAM for up to 10 years without refresh, and all without having to use a battery. The conversion is relatively painless and when done, no battery and no CONTROL BOARD ERROR ever again... that is unless the FRAM chip gets busted somehow, in which case the same errors will show up again. The nice thing about this is that fixing the problem now only requires spending a couple bucks to put a new FRAM in the socket.
PART 1...THE HARD PART...
You need to remove the existing RAM chip (U3) from the CPU board (A1). I do this type of thing by first cutting every lead on the chip leaving lead stubs sticking out of the board. This destroys the removed chip but who cares... it's history anyway. Next I grab the stubs with needle nose pliers, heat up the solder side of the lead with a soldering iron and pulling out the stub. I repeat this for all leads and then solder-suck the holes clean. Once this is accomplished I like to put in a chip socket, in this case a 28 pin .600 wide chip socket. Now you can insert and remove this chip without soldering, making it a blessing for some future repair man.
Repeat this process leaving out the installation of a socket with the Dallas NV controller (U6) and with the battery, simply unsolder it from the circuit board and discard it. Once these three parts are removed, the easy part comes.
PART 2...THE EASY PART...
Using 2 pieces of hookup wire (AWG28 SOLID or similar) jumper pin hole 5 to pin hole 6 of the hole pattern revealed by the removal of U6 and jumper pin hole 8 to pin hole 1 of the same pattern. The last step is to install a new FRAM chip in the U3 socket. I have found a direct pin for pin relpacement for the old 6264 CMOS RAM and that's the Ramtron FM1608-120-P which is a 64K 8Kx8 FRAM chip in a 28 pin, .600 wide spacing DIP case... THAT's IT!! plug the CPU board (A1) back into the pinball machine, and perpetuate the illusion that you are a smart guy!