Bally/Stern MPU Test Aid - Who Wants One?

Lindsey

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I've been working on some new hardware for the classic Bally/Stern system and I made up some boards to move the ROM from the original sockets to a daughter board that plugs into J5 on the MPU. The daughter board accepts 2 2732 EPROMs. This is a proof of concept for a future design which will use a single 2764 EPROM and move the 5101 RAM to the daughter board in NVRAM. I probably won't make any more of this version so get them while they're hot... and cheap. I have 4 available. Your choice of game code. $30 each. Shipped.

Caveat: MPU100 and Bally -17 MPUs don't have A14 connected to J5. This means that you can only use ROMs intended for MPU100 or -17 MPUs on those boards. I could have fixed this but like I said... it's a proof of concept design.

The ideal use for these boards (IMO) is for use with Leon's test ROM.

Who wants one?
 

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I tested this box of MPUs tonight with one of these boards in about an hour. That probably would have taken a couple of days jerking around trying to get code running in the original EPROM sockets. Most of these used 9316 ROMs so it would have been a huge pain to test them. All I can say is I wish I would have built these years ago. The next version will be even better! 2010 is going to be a great year!

The next version will still use 2x2732 EPROMs but it will have an on board reset circuit and LEDs for reset and A6 on the CPU (will flash with Leon's test ROM). That way you can easily strip down a board and test the CPU/clock circuit and install the other chips from there.

If anyone has suggestions for other improvements I would love to hear them.

If you work on Bally/Stern MPUs you need one of these. I still have a couple of this version available. I added a "test LED" on mine and it works awesome.
 

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This makes me very excited to receive mine. Looking forward to putting it through it's paces. I for one, appreciate you taking the time to make these.
 
I tested this box of MPUs tonight with one of these boards in about an hour. That probably would have taken a couple of days jerking around trying to get code running in the original EPROM sockets. Most of these used 9316 ROMs so it would have been a huge pain to test them. All I can say is I wish I would have built these years ago. The next version will be even better! 2010 is going to be a great year!

The next version will still use 2x2732 EPROMs but it will have an on board reset circuit and LEDs for reset and A6 on the CPU (will flash with Leon's test ROM). That way you can easily strip down a board and test the CPU/clock circuit and install the other chips from there.

If anyone has suggestions for other improvements I would love to hear them.

If you work on Bally/Stern MPUs you need one of these. I still have a couple of this version available. I added a "test LED" on mine and it works awesome.

The on board reset circuit is an excellent idea. I've had some (working) Bally MPU's not like to boot up reliably on the bench with a switcher. That should eliminate the issue. Excellent work.

Edward
 
The on board reset circuit is an excellent idea. I've had some (working) Bally MPU's not like to boot up reliably on the bench with a switcher. That should eliminate the issue. Excellent work.

Edward

Thanks :)

I'm planning to use a 150ms reset with a jumper to turn it on or off. I've had the same problem booting MPUs on a bench. I'm not sure if the switcher voltage takes more time to become stable than a linear supply or what the problem is but I find myself having to do a lot of manual resetting on the bench. I'm also adding a small button for manual reset.

Another nice thing about on board reset will be working on MPUs with a flaky reset section. I like to get the CPU running as a first step so the next version of this board should allow for a very direct approach to doing that.

This is going to be a great year. I've had several great hardware ideas over the last couple of years and they're finally starting to come together.
 
Adding the reset circuit....and a manual reset button.....I can't see anything else this design needs. It will make an excellent troubleshooting tool.

Now, if you wanna add a CMOS RAM or some other form of memory backup.....we could eliminate the entire corrosion area, and make repairs a breeze. :)

Edward
 
Now, if you wanna add a CMOS RAM or some other form of memory backup.....we could eliminate the entire corrosion area, and make repairs a breeze. :)

Edward

That is in the works. That's my ultimate goal actually. When I started testing MPUs with these boards I knew I had to add a couple of things and do a run of these intended for testing MPUs. The final product will be intended more to permanently replace all the RAM and ROM on the board rather than being geared toward troubleshooting.

I realize that TwoBits already has the same basic product but mine won't be exactly the same.

I'm also planning to design a board to use EEPROM in place of EPROM with a USB microcontroller to program the EEPROM. That will be mainly intended for people writing new game code but it will also be a handy test aid. It's a small market but I know the people who will actually use one will be thrilled. I already have boards made that replace the Motorola 6800 with a PIC microcontroller with USB. I'm hoping to come up with something that will allow people to more easily write new rules for games and add sound to a machine with a computer. Like I said... I've been thinking about this stuff for a long time and it's finally starting to happen.
 
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Well... after 4 months on the back burner I finally got around to running the new boards. They're basically the same concept as the original boards with some additions geared toward troubleshooting. I've added LEDs for +5V, CPU A6 (flashes with Leon's test ROM) and reset (on when reset pin is high). I also added a button for manual CPU reset and an on-board reset circuit that is switchable with a jumper. This reset circuit provides a longer reset cycle (150ms) than the reset circuit on the original MPU.

The biggest advantage to these boards (IMO) is the ability to run the test ROM without touching the EPROM jumpers on the MPU. This is especially helpful with MPUs strapped for 9316 ROMs. The on-board reset, manual reset switch and reset LED make troubleshooting the reset circuit on a bench much faster and easier. The LED on A6 of the CPU also makes troubleshooting with Leon's test ROM quick and easy because you can remove all socketed chips leaving only the Motorola 6800 CPU and start with the basics (CPU, clock and reset).

I also added an additional row of pads in parallel with the J5 connector pins. I won't be shipping these with header pins installed in these holes but the option is there to install .100" header pins. This is really only necessary if you're going to use the board in a Stern game with a sound board that connects to J5. These holes are also a handy place to add wires or even headers for whatever you can think of.

This board won't fix the MPU for you but it should make troubleshooting much easier. Especially if you work on a bunch of different MPUs.

You can still use these boards to replace the original game code but this version is really geared toward troubleshooting.

Price on these is $40 shipped. I will be accepting payments and shipping boards in about a week (waiting on some Dallas reset ICs). I only have about a dozen or so of these boards. PM me or post here if you want one. If there is enough interest I might do another run but then again I might not.

Questions? Comments?

Note: The final boards will have the on-board reset holes populated with a user selectable jumper. I don't have one installed in these pictures.
 

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PM sent as well - being able to quickly bypass the clock circuit with one of these will come in handy..
 
PM sent as well - being able to quickly bypass the clock circuit with one of these will come in handy..

This board doesn't bypass the clock circuit. Not sure where you got the idea that it did. To do that you would need a daughter board that plugs into the CPU socket. Only one half of the clock is available at J5. Even if the clock were connected to J5 there would still be no way to disconnect it from the CPU and drop in another clock circuit. The short answer is it's just not possible with a board that connects to J5.

I am planning a CPU socket version but I don't think I'll add a clock circuit. Once you've narrowed it down to just the CPU and clock on the board it's pretty easy to diagnose the clock circuit on board. I can see it making troubleshooting a little easier. If the thing starts working with the clock bypassed you know you have a clock problem but it's not something I would personally use so it likely won't be added.

Basically my direction is going to be selling these boards as a test aid and the CPU socket version to permanently replace the ROM and RAM. It's easier to implement a "universal" ROM and RAM replacement in a CPU socket version because I don't have to deal with -17 and Stern MPU100 boards missing the highest address line on J5. I could probably still make it work but I don't want to :)

Sorry I didn't get back to your PM. I was planning to respond to everyone when the boards are ready to ship. My order from Mouser is taking a little longer than expected but they should be ready some time this week.

Okay... I just looked at the schematic and I should have realized this right away but it's still not going to be possible even with a CPU socket based board because of the 02 signal goes not only to the CPU but out to some logic. It would be a real pain in the ass to try to build something to bypass the on-board clock and that's not a difficult circuit to troubleshoot once you've isolated the CPU and clock and you've got my board installed.
 
Well... there's good news and bad news.

Good news: My parts order arrived.

Bad news: They shipped me SOT-23 package reset ICs instead of TO-92 (what I designed to board to use).

They confirmed that this is an error on their website and I will get the correct parts. It's just going to set me back a while. Sorry guys.
 
Sorry; meant reset circuit, not clock circuit. Reset circuit frequently affected by acid, so bypassing it is very handy.
 
I got the reset ICs today (from digikey) and they are working really well. Adding the on-board reset, test LED and reset LED made these boards go from awesome to turbo mega awesome. From this point on I won't consider troubleshooting a dead Bally/Stern MPU without one.

They're ready to ship. PM or post here if you want one.
 
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