From: kcimming@pobox.com   
      
   On 1/9/2025 7:03 PM, Jan Ernst Voß wrote:   
   > But games build by Playmatic are special: they use CMOS instead of TTL   
   > logic.   
   >   
    > ...   
    >   
   > 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.   
      
   Debugging isn't much different with CMOS vs. TTL.  CMOS drives logic   
   high at ~4.4V vs. ~2.4V for TTL.  And older CMOS is more static   
   sensitive than TTL.   
      
   The switches that are working (coin, credit) are ones that are usually   
   on dedicated switch inputs.  The other game switches will be in a switch   
   matrix.  You should be able to measure logic voltage levels (a logic   
   probe would be helpful) to see the switch matrix respond to switch   
   closures.  Look at the input and output pins of the receiving CMOS chip   
   to verify switch activity.   
      
   - Kerry   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)