NeoGeo MVS power requirements

**bacteria** · 11-03-2009

I got an MVS NeoGeo board and two carts recently, wired up RGB and the three voltages (12v, 3v and 5v) however used a 7805 to step down for the 5v, and it clearly can't deliver. a 7805 can muster up to 1.5 amps, wasn't enough. I got lots of small coloured squared on the screen with some ASCII characters moving a bit. I presume the board is ok (hopes), just needs lots more amperage. Would a TI card suffice (5v at 2.25amps max)?

So, what amps do the three volt lines need please to work on the MVS please?

Is the issue mentioned above with the coloured blocks down to insufficient amps?

**alphagamer** · 11-03-2009

Depends on the board.

Some boards like the MV-1A need 5v 3amps 12v 1amp, the MV-1F needs 5v 5amps 12v 1amp (both according to specs found in official papers from SNK). And you don't need 3v on an MVS. You can try with 2 amps on the 5v line, 12v is only needed for audio amplification btw.

**bacteria** · 11-03-2009

My error - no 3v needed!

Just found datasheet here for the MV-1B board I have (single cart board), says it needs 5v at 3 amps and also 12v at 1 amp.

I'm wondering - would the power board from a DreamCast be enough to power the NeoGeo system? Spent a while on Google looking for the maximum power output of the DC power board, can't find details. Not sure if the DC power board can output 3+ amps?

**alphagamer** · 11-03-2009

The Dreamcast PSU might barely deliver enough power for an MVS board, and running a PSU constantly on the max is never a good thing.

**bacteria** · 11-03-2009

Thanks for the replies alphagamer. Sound.

Do you know of a step-down regulator that can take 7.4v or 12v batteries (Li-ion) and output over 3 amps at 5v? I know there are some about, however do you have any recommendations?

**alphagamer** · 11-03-2009

Maybe the LM 2576 -T5?

**bacteria** · 11-04-2009

The ones ending in "5" I presume are the fixed 5v ones.

Found this datasheet: HERE

Can't work out how to connect one of these up to get 5v from it, where the capacitors go, what's needed, etc. I'm not too great reading electrical diagrams! Anyone help?

**ccovell** · 11-05-2009

Got any junk shops around? I just recently bought an MVS 1F, and so I found a laptop PC power supply at a 2nd-hand shop that output 5V and 12V at 2 Amps each. Worked great after I found a matching connector for it.

**marshallh** · 11-08-2009

http://www.national.com/ds/LM/LM2576.pdf

The ref. schematic is right there on the first page. You only need a handful of parts to build it.

**bacteria** · 11-08-2009

Indeed, found that PDF, and bought the component, however can't understand what goes where on it, could someone explain what component goes to what please?

Looks like (running left to right): 7v+ in, 100uf capacitor to ground, pin 3 to ground, pin 5 to ground, not sure what the triangle with the squiffy is above it or what it is; what 100ph is in resistor terms, and finally a 1000uf capacitor.

Can someone please elaborate and correct my errors?

**Calpis** · 11-09-2009

D1 is a schottky diode. L1 is an inductor, not a resistor.

You don't need a fancy switching regulator for a handful of watts; you could instead just use a common 7805 with current pass diode/transistor. Personally I wouldn't go through the trouble to build a regulator at all since you can easily find a 5V supply.

**Jamtex** · 11-09-2009

2 Electrolytic caps, 1 diode and 1 inductor (not a resistor...). uH is microhenrys.

I wouldn't even think about using a Lithium Ion battery to power an MVS system as the current draw is likely to be in excess of what the battery can supply and they have a nasty habit of catching fire or exploding without a proper protection circuit.

**bacteria** · 11-09-2009

Jamtex - thanks. Li-ions I use have battery protection circuits, for that reason.

Looked on ebay - inductor and IN5822 the inductor is 5.4 amps, didn't find a 3 amp one (guess fine going over spec?), and the In5822 diodes seem to be 3 amp anyway.

These are the correct items, yes? I have the capacitors anyway, just not the two items above.

**_SD_** · 11-09-2009

I'm sure it's possible to mod certain MVS boards so that so you only need 5v. I can't remember exact details but I'm totally sure you can do it with an MV-1C. You can remove the audio amp and huge heat sink, run line level stereo and mod the board so you only require 5v power.

EDIT: Hurrah, I'm not insane! It is possible. The bods over at Neo-Geo.com have set up a wiki and have a page on it with nice instructions and pictures.

I've just realised you have an MV-1B. Maybe it's still possible to do the mod?

**bacteria** · 11-10-2009

No idea. When I start my NeoGeo project i'll read up on that forum and research.

**TheRogue** · 11-12-2009

Funny thing, whoever wrote that schematic used the wrong symbol for the Schottky diode. That symbol is for a resonant tunneling diode, the Schottky diode symbol is this:

I just thought I would point this out in case anyone got confused.

**channelmaniac** · 11-14-2009

Originally Posted by Calpis

D1 is a schottky diode. L1 is an inductor, not a resistor.

You don't need a fancy switching regulator for a handful of watts; you could instead just use a common 7805 with current pass diode/transistor. Personally I wouldn't go through the trouble to build a regulator at all since you can easily find a 5V supply.

I wouldn't use that 7805 with a current pass transistor. If the current pass transistor shorts out then you will have the full unregulated voltage going to the game board.

RJ