We all know that Konami manufactured wonderful arcade games but, you know, beautiful things are often complicated too.And surely their hardware is! This mainly because of the use of many custom chips with the most disparate functions and shape.
The ‘052535’ is one of them, used on countless PCBs of ’80-’90 :
The ‘052535’ is basically a 5-bit video DAC (one for each R,G,B color) in SIL package used to convert the digital signals of the palette circuit into analog, we can see its pinout and implentation in this snippet from Lethal Enforcers schematics:
During my repairs sometimes I had to replace faulty ones so why not reproduce this part too?Perhaps someone else did it already but i did it my way.
First of all I removed the black epoxy to expose the circuit and scan it :
The black squares are printed film resistors, the part on the left marked ‘LF’ is a NPN transistor in SOT323 package, the four SMD parts are zero Ohm resistors.I metered the printed resistors (but first I removed the soldered parts to avoid interactions), this was the result :
As you can see the Konami ‘052535’ is nothing more than a R-2R resistor ladder with the resistors values tipically doubled (starting from 2.5KOhm up to 43.50KOhm).The NPN transistor (I marked it as a BC848 but it’s a NPN general purpose one) is used in final stage to amplify the analog signal adapting it to RGB arcade standard.The circuit is very simple so it took few time to draw schematics of it and route them to a PCB which ended up with more or less the same dimensions of original part:
Sent it to manufacturer and after some time got the bare PCBs:
Here is the assembled reproduction, I used the legs from thru-hole components as pins which fit well in a female header:
Testing on board was successul, reproduction validated!
See you all to next project!