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Darksoft

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THIS IS A REPRODUCTION PROJECT MADE BY @caius ALL INFORMATION HAS BEEN POSTED WITH HIS PERMISION. CREDIT AND MERIT GOES TO HIM.

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

RSCN4061.jpg


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 :

056820_schematics.jpg


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:

056820_trouble_.jpg


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

Konami_056820_decapped.jpg


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 :

RSCN4059.jpg


Testing on a Winning Spike:


See you to my next reproduction project!
 

AlxUnderBase

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When i touch the original on my motherboard , fries my fingers very badly! I think its time to offer one to my GX motherboard
 
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