Recently I have been working on reproducing the MB112S146 custom chip for my friend BanjoGuyOllie.
This module is found on Arkanoid, Darius and probably some other titles too.
This has now been done and is available in the downloads section. It required the adapter board from ColinD but I will soon compile for MikeJ’s module too.
So far its only tested on Arkanoid but probably will never get a chance to test on other hardware.
It shares the same 20 pin SIL package embedding most of the analog sound system.Its function is to mix and pre-amplify both music and sound FXs :
Here’s how it look “naked” of its external coating:
Design is almost identical to its predecessor with the presence of two OP-AMPs (a dual and a quad one) although they operate from a single supply (+12V) and not dual (+5V/-5V) like the ‘HB-41’.All other components are ceramic/tantalum capacitors and resistors (surface mounted and printed film ones) which are part of the application circuit of the two OP-AMPs
It took some time to draw schematics not without some difficulty due the presence of some hidden printed film resistors located under the quad OP-AMP:
Schematics were then routed to a PCB which looked pretty good on a 3D preview :
The real thing assembled in all its parts :
For a while I was not able to test this reproduction due the lack of a working PCB (the “decapped” original part was taken from a dead board) until the user ‘opt2not’ from Arcade Projects and KLOV forums kindly volunteered.The test platform was his working Raiden DX PCB.He first removed the original ‘HB-45A’ in a very clean way (he used an Hakko FR-300 desoldering gun)
Installed some female 2.54mm round machined headers:
Lastly the reproduction fitted onto the board:
Then he made recordings of audio of both original custom and reproduction redirecting it to a PC from a HAS supergun using a SPDIF breakout from the SCART connection.
Here ‘s capture using the original HB-45A:
Here’s the one using my reproduction:
Comparing the music and FXs at the beginning and end of the recordings sound identical.No differences in quality can be noticed (the slight background noise is normal when there is silence).
For this successful reproduction project I would like to thank again ‘opt2not’ for his precious testing and all material (pictures and audio captures) he provided me.I recommend you to check out his blog :
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:
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 :
The Konami ‘054573’ is a custom chip found on various PCBs from this manufacturer : Bucky O’ Hare, Metamorphic Force, Gaiapolis, Xexex, Mystic Warriors, Wild West C.O.W. Boys of Moo Mesa to name some.Technically speaking it’s a RGB DAC (one for each color) which converts into analog the palette data bits received from the the custom ASIC ‘054338’. There are no schematics showing it but it should be a 9-bit DAC .
It comes in the usual SIL package (15 pin) covered by black coating like many custom with similar functions :
I have partially covered this topic in a past repair from mine, where you can see also picture of its circuitry inside :
Being a important and not long reliable part I decided it was time to think of a replacement.No particular difficulties were encountered in identifying the internal parts, tracing connections and developing a PCB which arrived from my manufacturer after some time.Here’s the reproduction finally assembled and installed :