5101 SRAM chip blues

I made a new 5101 SRAM board, and we tried it in Flash last week.  When I made the board, I remembered some of the people on the pinball boards saying that the second chip enable was not needed.  Ooops, should have take the time to download the schematic.  Looking at the schematic, it immediately became obvious that I did need the active high chip enable.  Very disappointing, and it did mean that we wouldn’t be able to get past this issue on 4/17/2012.  I went back to the drawing board and came up with a way to create the extra chip enable using a FET.  Of course, in that time, I was also looking around Mouser and found an Alliance memory chip that had both of the chip enables  (AS6C6264A).  It goes for about $1.54 in quantities 1.  That meant making another board, and spending the time to drill it out, and solder the new connectors.  Jumped back on the internet and ended up running into www.arcadechips.com.  They had actual 5101 RAM chips for $4.50 which is about the same price as the parts that I needed to make my RAM replacement.  When it would have been $20 for the chip, it made sense to update the design, but now, doesn’t seem to make much sense.  Now the only thing that makes my design better is that it takes less current to hold the memory.  Not a good enough reason, so I’ve just given up on this sub-project.  The RAM chips should come in this week and we should be able to test them next Tuesday.  Hopefully that will give us enough time to find any more problems before going down to Allentown for the pinball show at the beginning of May.

First rev of the boards for the open pinball project is getting pretty close.  More on that when I finish them, and figure out how to put the schematics up on the web.

The Restoration Page

The open pinball project also needs to deal with old machines many times.  I ended up buying three machines last year, (well maybe four or five depending on how you count them), and set about restoring them.  Best way to understand the things that are necessary in a pinball machine is to try and work on a couple of old machines that just don’t work at all.

The original machine was Williams Olympic Hockey.  This is an old EM machine with a nice backglass animation.  Got the machine for a fair price, and it was a good introduction to pinballs.  Within a month or two, I had the machine up and running about 95%.  It was very playable, so I just stopped working on it, and started doing other things.  I still want to get back to it and fix it up fully.  I understand so much more about pinball machines that I could do a much better job on it.  The basic fixes involved readjusting switches, and reversing many of the “enhancements” that a previous owner had done to try and get it to work.

The next machine was a Tropic Fun EM machine.  The playfield was trashed.  This machine should have gone to the great pinball arcade in the sky, but we decided that I wanted to learn how to restore playfields.  We learned a lot on this machine and it is currently being clear coated.   In the next month or two we should be putting this puppy back together.

The next group of machines were three solid state machines.  These included a Bally Dolly Parton, Bally X’s and O’s, and Williams Firepower II.  We restored X’s and O’s first since it was in the best shape.  Got it up and running for New Years Eve so that Mark could play it over Christmas.  We currently plan on selling this machine off for about $600.  If anybody is interested, post a comment.  Was hoping bring it to the pinball show in Allentown, but don’t know how long I will be there, and don’t want to waste my time trying to sell a machine.

Next came Firepower II.  We finally got this one up and working by fixing many connectors, stripping the playfield, doing a complete cleaning, replacing some of the mylars that were lifting, fixing some of the targets that were broken.   We played it for a few months, and now we are trying to fix the smaller things that are annoying, but don’t necessarily hurt the play.  This is by far, the machine that we play the most.

Dolly, oh you sad, sad girl.  The playfield is trashed.  The backglass is trashed.  I had it working for a while and it just gave up when I tried to fix it.  I’m working on this one by myself in my free time, and it has been slow going.  Hopefully this will be working in the next couple of days.

Last machine is currently Williams Flash.  We bought this from a guy in NY and it has been a complete pain in the butt.  Really learning a lot about debugging old Williams boards.  I will hopefully be posting some of the stuff that we have learned on this page.  We have a nice design for using a new SRAM to replace a 5101 SRAM that can’t be bought easily/cheaply anymore.  We also have a design that contains the EPROM code and the test EPROM code for the Williams board in a single package so that just switching the jumper allows you to go between these two pieces of code.  That also involved building an EPROM burner over the weekend so that we could program the flash.  That is all for today.  I will try to post more information on the above projects so that others can build them themselves.  Hey, it isn’t called the Open Pinball Project for nothing.

And so it begins…

This blog will be  a repository for information on building the open pinball project.  “Open” because the design is going to be placed out on the web so that you can build the machine yourself.   My dream is to build ten of these machines and to make the design open enough so that the hardware can be reused on virtually any machine that can be dreamed up.

The machine is going to use custom hardware and custom software.  The architecture consists of a main processor, solenoid driver boards, input boards, LED lighting boards, and a display driver board.  The processors can be configured for many different pinball games.  Each one of these elements will be described more fully as the design progresses.