I received for repair a quite rare original Spelunker PCB (on Irem M62 hardware).Board is a three stack one made of a top board (which carries most of sound hardware) :
![](https://www.jammarcade.net/images/2018/12/top.jpg)
A middle CPU board (specific for each M62 game) :
![](https://www.jammarcade.net/images/2018/12/middle.jpg)
And a bottom VIDEO board :
![](https://www.jammarcade.net/images/2018/12/bottom.jpg)
The PCB had severe GFX faults, the sprites were only lines vertically stretched all over the screen:
All the sprites circuit lies on bottom VIDEO board which is the same for all games that run on M62 hardware.Looking at Kung-Fu Master schematics I could figure out that data bits from sprite ROMs are fed into the custom marked ‘KNA6034201’ :
![](https://www.jammarcade.net/images/2018/12/DSCN5986.jpg)
![](https://www.jammarcade.net/images/2018/12/KNA6034201_schematics.jpg)
The inputs were all active but most of outputs floating:
![](https://www.jammarcade.net/images/2018/12/KNA6034201_scope.jpg)
So the custom was most likely internally faulty.Luckily I have done a reproduction of this component some time ago.You can think of it like a 24-bit parallel to serial shift register:
I removed the custom and installed the reproduction:
![](https://www.jammarcade.net/images/2018/12/KNA6034201_repro_installed.jpg)
The sprites were back but not perfectly as they were lacking of lines and misplaced too:
![](https://www.jammarcade.net/images/2018/12/sprites_back.jpg)
The sprite line buffer consists in two 2k x 8-bit static RAMs (Toshiba TMM2018 used here) :
![](https://www.jammarcade.net/images/2018/12/sprite_line_buffer-1.jpg)
Probing them revealed on both a floating address line (pin 1, A7) :
![](https://www.jammarcade.net/images/2018/12/floating_A7.jpg)
Address lines are generated by the surface mounted custom ‘KNA6074601’ :
![](https://www.jammarcade.net/images/2018/12/RSCN6391.jpg)
Its pinout/implementation from Kung-Fu Master schematics :
![](https://www.jammarcade.net/images/2018/12/custom_KNA6074601_schematics.jpg)
I had no other choice than replacing this part so I asked the owner to look for a donor board.He found and sent me a Vigilante PCB which carried the ‘KNA6074601’ on bottom board :
![](https://www.jammarcade.net/images/2018/12/Vigilante_donor.jpg)
I removed the faulty one and soldered the spare back :
![](https://www.jammarcade.net/images/2018/12/custom_KNA6074601_reworking.jpg)
This restored the correct sprites:
![](https://www.jammarcade.net/images/2018/12/fixed-1.jpg)
Board 100% fixed.Job done.
Sorry, the comment form is closed at this time.