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Main => Main Forum => Topic started by: Savannan on September 23, 2011, 05:10:09 pm

Title: Need help! How to get -5v out of newer ATX Power Supply's
Post by: Savannan on September 23, 2011, 05:10:09 pm

Hi all...

I need help...I picked up a cosair 600w power supply today for my multi-mk cab.   Everything was going good but I was looking at the Pinouts on the 24pin connector and it doesnt have -5v pin.  /cry   

I looked at wikipedia and found this
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Pin 20 (formerly −5V, white wire) is absent in current power supplies; it was optional in ATX and ATX12V ver. 1.2, and deleted as of ver. 1.3.

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Is there a mod that I can do get achieve -5v out of this power supply? Or would I have to buy a older P/S?

Thanks!!!!!

Sav

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: BobA on September 23, 2011, 06:30:48 pm

You can use a -5v regulator to get 1A -5V from your -12V supply.

Google LM7905

 :D

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: Thenasty on September 23, 2011, 09:46:43 pm

Quote from: Savannan on September 23, 2011, 05:10:09 pm

Or would I have to buy a older P/S?

Thanks!!!!!

Sav

No need to buy

http://forum.arcadecontrols.com/index.php?topic=101280.0 (http://forum.arcadecontrols.com/index.php?topic=101280.0)

also in the FREE Section

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: Franco B on September 24, 2011, 04:46:00 am

For Jamma boards that require -5v I have used a Negatron wired to a Jamma pass-through. It may not be the solution for you but its worth noting for reference.

(http://img.photobucket.com/albums/v325/Francoberasi/negatron006-1.jpg)

 

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: Savannan on September 24, 2011, 10:17:49 am

whta does that negatron do?

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: Franco B on September 24, 2011, 10:31:18 am

Its a DC-DC convertor. You can input 4v to 14v and output -1.3v to -12v

I have the input wired to the 12v of the Jamma edge and the output set to -5v and wired to the -5v pin which provides 0.5A

I used it for games that require -5v for the audio amp as the PSU I had didn't supply -5v.

More details [here (http://www.dimensionengineering.com/negatron.htm)]

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: Savannan on September 24, 2011, 11:15:53 am

Wow..it sounds like its the thing I need..
But just wondering if it will work if I soldered that to my main jamma harness...plugged it into my 6 in 1 switcher and ran a midway game....?  Hmmm...
It would suck If I need one of these per game.

Sav

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: BobA on September 24, 2011, 02:20:01 pm

A negatron costs about $20 and if you need one for each board it is quite pricy.  An LM 7905 is about $2 and with the 2 caps needed comes in less than $3.

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: Franco B on September 24, 2011, 04:36:30 pm

I don't suppose you could provide a wiring diagram/parts list for the LM 7905 solution could you BobA, I would love to see it.

Title: Re: Need help! How to get -5v out of newer ATX Power Supply's
Post by: BobA on September 25, 2011, 02:01:49 am

Quote from: Franco B on September 24, 2011, 04:36:30 pm

I don't suppose you could provide a wiring diagram/parts list for the LM 7905 solution could you BobA, I would love to see it.

Here is the data sheet with sample circuit.