May 032021
 

A fellow collector gave me a Yie Ar Kung Fu bootleg in exchange for some work I did on some PCB’s. On powering up the board I noticed a number of issues:

  1. No Sprites
  2. Colours Wrong
  3. Left Input not working
  4. Missing a sound

I thought the colour issue might be related to the prom @ G20. One thing I noticed that the edge connector was really dirty so I gave it a clean with a pencil rubber, and connected the board up and the left input, colours and missing sound were now working. No Sprites visible still.

As there are no schematics for a bootleg Yie Ar Kung Fu, I had to draw out all the connections to help me find the fault.

I knew that the Sprites were located in roms 3-6. Everythng was good on the address and data lines on the sprite roms so I followed the output and inputs through the LS194’s @ H3-6, and then through the 157’s @ H1-2. This led to LS32’s @ B2/C2 and and an LS74 @ A1. I could see no signal on pin 9 of A1 and this led me back to an LS04 @ B1 pin 2. I could see activity on pin 1 but nothing on pin 2. I suspected this had failed. I removed the chip carefully and verified that the IC had indeed failed . Swapping the chip restored the sprites to the game 🙂