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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.

Picked up recently this cheap untested Gals Panic PCB (MCU protected version)



When powered up I was greeted by this :



All inputs (including SERVICE) are handled by a custom in SIL package marked ‘MC-8282’ (found also as ‘MC-1091’ in other boards from Kaneko)



I’ve already discussed the topic in my past post about the reproduction of this custom:

https://www.arcade-projects.com/for...‘mc-1091-mc-8282’-reproduction-by-caius.4773/

Most likely the component was internally faulty so I replaced it with a repro of mine:



Finally the board booted into game but the sound was barely audible also at maximum volume:


After a visual inspection I found that the component silkscreened ‘PX4460’ was missing from sound section:



Board uses also another little sound custom, the “LPF6K”, here is a picture from another board for better understanding:



Actually you can replace themby installing the parts they are internally made of directly on PCB (there is silkscreening for them) but I wanted to keep the all-in-one solution the so I decided to have a look inside them in order to reproduce both (although the ‘LPF6K’ was not missing on my board).I removed the coating and did an Hi-Res scan;



On the right on the above picture it’s the naked ‘PX4460’ which, like its name suggests, embeds all the parts (minus the 1000uF 16V electrolytic capacitor, this is on the PCB) needed by the typical application circuit of the ‘LA4460’ amplifier as datasheet shows :



On the right of the scan, it’s the ‘LPF6K’ that contains an LM324 OP-AMP and all its required parts, its function is to pre-amplify the sound.
Given the simplicity of both customs it took few time to figure out schematics and route them to a replacement PCB.Here is the result:



Installed on PCB ready for the smoke test:



Success!Sound was restored and both repro worked fine as replacement.

 

Apocalypse

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Thanks.Yes, too many reproductions perhaps and other are coming... ;(
I see it as a very good thing regarding hardware preservation.
Ideally I'd like all customs to be reproduced (yes that's a hell of a job).
 

caius

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Ideally I'd like all customs to be reproduced (yes that's a hell of a job).
Me too.And when I speak about customs I mean reverse-enegineering of digital ASICs, there are a lot of them.But this involves a different approach and superior skills.Mine are only simple reproductions... ;(
 

caius

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I think some ASICs can be decapped (might be easier/cheaper than complete reverse engineering).
Sure, I mean reverse-engineering assisted by decapping.Saldy most of times decapping is not enough when you have some million of transistors in multiple layers...
 

Apocalypse

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I think some ASICs can be decapped (might be easier/cheaper than complete reverse engineering).
Sure, I mean reverse-engineering assisted by decapping.Saldy most of times decapping is not enough when you have some million of transistors in multiple layers...
Millions of transistors?
The M68000 CPU is named after the number of transistors in its core (around 68000).
I don't see custom ASICs from 20 or 30 years old arcade boards being more complicated than a CPU of the same period.
 

Apocalypse

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It was an hyperbole.Take for example the '054321' ASIC, perhaps there are no million of transistors in it but neither some dozen.. :)
I know Italians are great fishing stories tellers ;)

Anyway we should really tackle that '054321'. I have my poor Xexex laying next to me...
 

caius

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I know Italians are great fishing story teller
Me italian?I feel I have very few from this country... :D
Anyway we should really tackle that '054321'. I have my poor Xexex laying next to me...
I know someone is working on its reverse-engineering.I have reproduced some functions with simple logic gates but I've been told the most difficult part to figure out is the volume handling since this ASIC rules this aspect too.
As for you Xexex, you can always buy a repro from mine... :P
 

fluxcore

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Love your work Caius, nothing better than seeing custom hardware getting open source alternatives IMO :D
 

Apocalypse

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Never encountered a faulty '054321', they seems robust.Does you board pass the self-test on boot?
Yes it does, graphics work so as controls but board is completely mute.
Pre-amp and amp are good.
Might be something related to the volume control.
 

invzim

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Nice! As it has an electrolytic, I guess it's just a matter of time (arguably long depending on use) before they commit seppuku.

Got a trick for 'decasing''?

A trick you may consider for future projects is to put rounded corners on the PCB - that way the PCB house more often than not route out the boards instead of using v-scoring to give you smooth edges.
 
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