This project started when, during my repairs, I came across these two PCBs.
Both were faulty.Blood Bros played blind :
While Raiden lacked of the BLUE color:
The culprit was the same in both boards, the ‘UEC-52’ (sometimes silkscreend on PCB as ‘HB-52’):
It was clearly faulty in Raiden and missing at all in Blood Bros:
This custom in SIL package is an RGB DAC responsible to convert the digital signals of color palette circuit into analog, it’s used on some Seibu/TAD Corporation PCBs like :
- Blood Bros
- Sky Smasher
Some time ago I partially figured out the pinout and schematics/parts after removed some of the epoxy resin that encapsulate it:
As you can see it’s a 15 bit DAC whose design resembles the Taito ‘TC0070RGB’ : two octal D-type flip-flops , some printed film resistors (with typical values of 4K, 2K 1K, 470 and 220 for the 5 bits of each color) forming resistor ladders before the output to JAMMA RGB pins.But there was also a third IC that I could not identify.At first glance I thought about some kind of darlington array to amplify the signals so I made a post on EEVblog asking for some help:
The user ‘stj’ (thanks again to him) pointed me in right direction suggesting that the unknown IC could be a 74LS367 used for video blanking.So I removed the IC from a working custom and was able to identify it as a 74HC368:
At this point I had all the info to complete my schematics in order to design a replacement, obviously I first made some prototyping on breadboard which went fine.Later I sent my project files to China for manufacturing and got the bare PCBs after some weeks:
Time to populate (in my design I used 74HC574 since it has more logical pinout compared to 74HC374)
Here is a side-by-side comparison:
Testing was successful on both boards (excessive brightness of recordings is an issue of camera, video levels are exactly the same of original part)
See you to next reproduction project!