custom ‘KNA6034201’ reproduction (R-Type) by Caius

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    • custom ‘KNA6034201’ reproduction (R-Type) by Caius

      THIS IS A REPRODUCTION PROJECT MADE BY @caius ALL INFORMATION HAS BEEN POSTED WITH HIS PERMISION. CREDIT AND MERIT GOES TO HIM.

      Got some months ago in a trade this pretty mint original R-Type board:

      Board was faulty, it was stuck on this static screen:

      System is made of three boards:

      ROM board



      CPU board



      Video Board:


      Swapping all the boards with a good set I could figure out that none of mine was properly working.So I started to troubleshoot the ROM board since it’s the most simple.The program ROMs were dumped as good but I found a bad 74LS245 @1A:

      This gave me a working ROM board and a good starting point so I moved on to troubleshoot the CPU board.Analyzing the NEC V30 (uPD70116) main CPU revealed the interrupt line was asserted (active high on this CPU), here’s a screenshot from my scope triggered with RESET signal

      The interrupt is generated by the uPD71059C;
      Interrupt Control Unit, probing it revealed that input pin 3 (READ STROBE) was stuck low :

      This comes from output pin 12 of a 74LS244 @IC72 :

      I pulled it :

      It failed the out-of-circuit testing:

      Finally the board booted but with multiple issues.First noticeable one was a totally missing sound but this was because the analog audio section was modified (by factory) to work in Nintendo cabinets.I simply reverted the mod by installing the missing capacitors @C101, C102 an C108 and removed the jumper wire:

      All the other issues concerned the graphics.Some examples:



      Honestly it would take too long to explain in details what I did (and maybe I even lost track of it…) before the board worked fine again :


      All I can say is that I had to replace;
      in total 15 TTLs (all from Texas Instruments, are we facing another Fujitsu perhaps?)

      But I claimed victory too soon , the board went bad again showing jailbars all over the screen:

      I quickly pinpointed this further failure in one of the two ‘KNA6034201’ custom tiles generator on video board:

      Testing it on a Kung-Fu Master PCB;
      (where it’s used for sprites too) gave me confirm it was really bad :
      Looking at this PCB I noticed that the other custom ‘KNA6034201’;
      was replaced by a little sub-board:

      Technically speaking the custom acts like a big shift register, it can take up to 24 bit of data from tiles or sprites ROMs, here’s snippet from R-Type schematics;:


      As you can see in the sub-board picture above the custom functions have been reproduced using six 74LS166 with common shift load and clock signals.So I wondered myself : why not reproduce it in a more modern way?I fired up my CAD and drawn schematics :

      Routed them to a PCB layout :



      I sent files to manufacturer and after some time I got the bare PCBs:

      Here is the final result compared to orginal custom:

      Luckily I made no design mistake and testing was 100% successful.Another board repaired and another custom IC delivered to eternity!
      * Arcade-projects, the site where you get the most of your arcade games.
      * If you want Drama go to Neo-Geo forum ---Darksoft
    • I have to get a couple of these as spares, my R-type board suffered the same failure on that IC, thankfully a friend had a parts board and was able to replace it and get my board working.


      Wanted:
      Cabs/Parts - Egret II, Forgotten Worlds PCB/Spinners
      Pinballs - Stern Star Trek / Metallica, The Simpsons PP, Medieval Madness