May 152018
 

The Konami ‘056820’ is a custom IC in SIL package (13 pin with an unusual 2mm of pitch) used on GX System  hardware:

Sometimes it’s wrongly reported to be an RGB DAC but if you look at his pinout (from Lethal Enforcers II schematics) you can understand it has a different function although always related to colors generation :

Its particular feature is that it gets extremely hot and may fail as a result.Here’s a picture taken from the net where the coating literally melted due excessive hot:

Driven by a curiosity I decided to take a look inside:

The biggest component in the upper left corner of the above picture is a Toshiba TA78M05F fixed voltage regulator, datasheet here:

http://www.jammarcade.net/files/Datasheets/TA78M05F.pdf.PDF

It provides on its output the +5V (regulating from +12V) to nearby custom ‘056766’which is actually the DAC  (specifically it powers the analog section of it since digital one takes the +5V from JAMMA connector).This explains why the part gets burning hot since the radiating surface of the heatsink (actually the copper of the PCB) is too small and not adequate in my opinion.All other parts are SOT-23 PNP transitors for amplify the RGB channels,   capacitors (for decoupling and voltage regulator stability) and printed film resistors, in particular there are thre 75Ohm ones to bring the RGB signals to the standard impedance level.The custom was pretty easy to reproduce, the only precaution I took in design was to enlarge the heatsink surface on the footptint of the voltage regulator.I used an MC78M05 in DPAK package since the original part is nowadays obsolete :

http://www.jammarcade.net/files/Datasheets/MC78M00_series.PDF

This granted me a better heat dissipation.Here’s the assembled reproduction :

Testing on a Winning Spike:

See you to my next reproduction project!

 Posted by at 2:48 pm

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