What's the deal with neo-geo and 12v?
- Thread starter Buffi
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- Oct 30, 2003
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Xian Xi said:
You could always drive speakers off the Headphone amp...
I've seen it doen..
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http://img84.imageshack.us/img84/10/92429215eq3.jpg
This pic shows the three things on a 2-slot board that run on +12v: the power audio amplifier HA13001, the voltage regulator 78M05 and the coin counter driver ULN 2003. The latter has no use on a consolized unit whereas audio for a consolized unit is better taken from the headphone circuit which is independent of the amplifier. The 78M05 however is used to convert +12v into +5v for a few op-amps (4558 in the pic above) as well as the DAC (YM3016) in the audio circuit. The trick is to remove the 78M05 and supply the op-amps and the DAC with the main 5v rail.
This can also be done on the other MVS boards that have the 78M05. Some are even easier in that they don't have the 78M05 and already have a unified 5v plane while some other are more difficult but all can be modded to output line level audio with 5v alone.
This pic shows the three things on a 2-slot board that run on +12v: the power audio amplifier HA13001, the voltage regulator 78M05 and the coin counter driver ULN 2003. The latter has no use on a consolized unit whereas audio for a consolized unit is better taken from the headphone circuit which is independent of the amplifier. The 78M05 however is used to convert +12v into +5v for a few op-amps (4558 in the pic above) as well as the DAC (YM3016) in the audio circuit. The trick is to remove the 78M05 and supply the op-amps and the DAC with the main 5v rail.
This can also be done on the other MVS boards that have the 78M05. Some are even easier in that they don't have the 78M05 and already have a unified 5v plane while some other are more difficult but all can be modded to output line level audio with 5v alone.
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- Mar 8, 2002
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Buffi said:
If it's the newer/smaller model (3 interconnects between bottom and top board and joy ports beside DIP switches) then it has no 7805 and you'll get sound off the headphone connector with 5v without having to do any hack.
If it's the older/bigger one (4 interconnects) do as follows:
- remove the 7805 (unscrew it, bend it so it stands up vertically and either wiggle it until its three legs break off or just desolder it).
- locate the area in the pics below and with a small flathead screwdriver (jeweller type) scrape off the green coating in the point shown until the copper is revealed. Tin that point and make a solder bridge with the nearby pin:
http://img232.imageshack.us/img232/7064/s2022160zq4.jpg
http://img154.imageshack.us/img154/5307/s2022161qr6.jpg
Done. Now you'll have headphone sound with just 5v.
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Xian Xi said:
4 Slot takes some real juice...
But a 2 slot can do it on 2 amps..... 2.5 to be safe...
Want a Neo Geo AES PSU (5v@3 amps)?????
I 've got one I can add to your order... It will support a 2 slot just fine....
LMK