From: kcimming@pobox.com   
      
   On 1/23/2025 10:00 AM, John Robertson wrote:   
   > On 2025-01-09 5:03 p.m., Jan Ernst Voß wrote:   
   >> Thanks for your replies!   
   >>   
   >> To say the truth, i am not really new to this group, but that's been   
   >> more than 30 years ago.   
   >>   
   >> Over the time, i owned 67 pinball games, all of them but the first   
   >> one, a Gottlieb's "Super Soccer" had failures. I've searched the   
   >> "Super Soccer" about a zillion to find the bad zero switch at the drum   
   >> units. I was 15 at this time, now i'm 62 years old.   
   >>   
   >> I repaired more than 100 machines, EM and SS as well.   
   >>   
   >> But games build by Playmatic are special: they use CMOS instead of TTL   
   >> logic.   
   >>   
   >> I bought a Big Town in 1987. The price was cheap, 70 DM (around 35$).   
   >> Both RAMs, both ROMs, and the CPU were dead.   
   >>   
   >> And other chips on the MPU were dead. I was able to get another   
   >> machine month later. It had good ROMs. This game was cheaper, 50 DM   
   >> (around 25$). I build a small circuit, using just 8 IS to do the job   
   >> of the 1834 ROMs.   
   >>   
   >> The ROMs were replaced by an EPROM 2716. The game went in attract mode   
   >> at once. Both games had a bad 74C42 on the decoder.   
   >>   
   >> Due to my job, i know most assembly languages of former machines. The   
   >> knowledge about these, i've made a "diagnostic board" for the   
   >> Playmatics, which was very helpful to find errors in the MPU of the   
   >> games.   
   >>   
   >> Now I have 2 bad "Big Town". Both are faulty.   
   >>   
   >> 1) Does not recognize contacts other than the coins, the credit, the   
   >> ball resting, reset, and the test buttons.   
   >>   
   >> 2) Shows irretating scores. "20" is the high score to date, new games   
   >> start with 200.020 points.   
   >>   
   >> That's it.   
   >>   
   >> Kind regards,   
   >> Jan   
   >   
   > Hi Jan,   
   >   
   > Wow, that is an unusual MPU and wiring diagram for we North Americans!   
   > I'm going by manuals and schematics I downloaded from ipdb.org -   
   > specifically Antar for the theory and schematics and Chance for the   
   > overall MPU diagram.   
   >   
   > The Antar schematic shows that the switches that are working share a   
   > common return line (page 24 of 35 in download Antar manual PDF) - so I   
   > suspect that you have an issue with other returns - and a logic probe   
   > that is happy with CMOS should help here.   
   >   
   > And as for the '20' on your display, I assume you have tried clearing   
   > the 5101 CMOS RAM (disconnect battery overnight - worst case clear), so   
   > it may be time to find a replacement RAM that is known-to-be-good.   
   >   
   > John :-#)#   
   >   
      
   Thanks for the schematic pointer John.  I was wrong in assuming the   
   logic would look like the Bally boards.   
      
   It's really hard to figure out all the connections from that schematic,   
   but it looks like the switch matrix is on page 30 of the PDF.   
      
   The best I can tell, that CD4021 shift register is used to cycle through   
   the four switch returns.  That's where I would start checking.   
      
   - Kerry   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)