NES:Famicom Disk System Glitching Sprites Fix

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Certain combinations of Famicom and Famicom Disk System (FDS) RAM adapter units have an issue which causes sprites to appear glitchy due to interference on the FDS RAM cart pins. The issue seems to affect mostly Famicoms made in 1989 and RAM adapters with boards marked "HVC-FMR-03" and some early "HVC-FMR-02" boards. Information for this guide was compiled from multiple sources.[1][2][3][4]

Sprite issue affecting Mario.
After sprite issue fix.


Solution

The solution is to add resistors on the data pins of the FDS RAM cart unit, which fixes the interference.

Fully installed fix.
  1. Obtain a 9-pin 4.7kohm resistor array.
    • Alternatively, you can use eight 4.7kohm resistors.
  2. Use electrical tape to line up the resistor array as shown and hold it in place.
  3. Bend the first pin of the resistor array upwards so that it doesn't make contact with anything on the board.
  4. Solder a wire between the first pin and ground. Example ground point shown in image to the right.
  5. Solder pin 2 of the resistor array to pin 6 of the FDS RAM adapter.
  6. Solder the remaining pins of the resistor array to the FDS RAM adapter pins. Pins 6-13 should all be soldered to.


References

  1. ↑ https://retro.supermegabyte.com/2018/07/23/fix-glitchy-famicom-disk-system-sprites/
  2. ↑ https://www.famicomworld.com/forum/index.php?topic=10607.0
  3. ↑ https://synt4x.org/blog/index.php/2018/01/19/glitchy-graphics-on-famicom-disk-system/
  4. ↑ https://twitter.com/SuperZvesda/status/1639694888944951297
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