The Konami ‘503’ is a custom chip we can find on some PCBs from this manufacturer.It comes in a DIP40 package with its part number scratched off in typical Konami style :
You can refer to this spreadsheet (courtesy of user ‘mattosborn’ on KLOV forums) for a list of boards (all with Konami Classic pinout) that carry this custom :
Technically speaking, the IC takes care of part of the sprites handling (along with the other custom ‘502’) as schematics shows :
We already have a modern replacement of the Konami ‘503’ thanks to the wonderful work of people over FPGAArcade forum, this is the thread of reference :
What I made is a “poor man’s” reproduction of this custom chip with no use of CPLD or other complex programmable logics but I simply re-engineered with surface mounted devices the replacement daughterboard (silkscreened ‘KC001’) that Konami used in place of the IC :
Here’s the result:
It works fine on my Track & Field and Kicker PCBs and should do the same in all other boards except Gyruss which requires a couple of functions not implemented in the replacement board (hence on my reproduction too).