No announcement yet.

Smaller Paddles = Bigger Fun


Share any logs or helpful information you may have to repairs of arcade PCBs, Monitors etc

  • Filter
  • Time
  • Show
Clear All
new posts

    Smaller Paddles = Bigger Fun

    The Kelso Mod

    Original Paddle Size:

    Modded Paddle Size:

    I saw this mod a while ago and decided to knock it up and see if it works.
    Most of the info below has been copied from here...

    In season 1 Ep22 of That 70's Show, Kelso mods a Pong to make the paddles smaller.
    If you play Pong for a while it can get a little boring especially if there are two equally skilled, good players.
    This mod adds another level to the difficulty.

    Game play video:

    Video explaining the inspiration:

    Paddle 1 Control - Original Schematics

    Paddle 1 Control - Modded Schematics

    Getting smaller paddles is fairly simple (if you understand digital electronics). In normal operation the 555 timer is triggered by vertical blanking, delays for a time set by the players control, then triggers the 74LS93 4-bit counter. The counter increments every horizontal sweep, from 0 to 15 (total 16); from 0 through 14 the NAND output is 1 which means the paddle is drawn on screen. On count 15 (binary 1111) the NAND output goes to zero, stopping the counter and the drawing of the paddle, therefore the paddles are 15 vertical pixels long. Signals B, C and D are used to calculate where on the paddle the ball collided, which sets the return velocity. This process is re-triggered every 1/60th of a second by the vertical blanking.

    To get smaller paddles:
    Signals B, C and D now use the lower 3 bits (weighted 1-2-4) of the counter instead of the upper 3 bits (weighted 2-4-8). The NAND stops the counting at 7 (binary 111) instead of 15. Thus the paddles are 7 vertical pixels long. In theory, the paddles could be set to any number of pixels from 1 to 15.

    Here's the mod itself..

    Last edited by Kaizen; 17 January 2019, 08:28 PM.
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3
Users Viewing Topic: 0 members and 1 (guests)