Negative power

Thread Starter

danrulz98

Joined Sep 17, 2012
15
Hello,
I'm trying to find a replacement power supply for an old game machine. The original is a giant brick, and I think a modern switching power supply can fit inside the unit its self.
But, I've been searching around and I can't really find a solution.
I need:
+ 12 volts at 0.3 amps
+ 5 volts at 0.9 amps
- 5 volts at 0.1 amps

and all sharing a common ground.

I was thinking I could use one of those generic 12 volt power supplies and a LM7805 and a LM7905, and while that would provide the + 12 and +5, the LM7905 just doesn't work that way.

Since the 3 of those share a common ground, I don't think I can run the 5 volt supplies off of the 12 volt supply at all.

So now I'm wondering what my best option is? To use a little 12 volt power supply and two iPhone chargers (5 volt very regulated power supplies)?
Ideally, I'd like to have just one power supply that can provide all of that. It's not a whole lot of power that's needed, especially on the -5 volt rail.

I'm just looking for the simplest answer at this point.
Thank you!
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
How come it was a 'Giant Brick' for that small a VA?
You can get wall wart types that will cover that current for <$4.00.
rig three of them up, 1-12v 2-5v with a short power bar or 4 socket surface mount outlet box, and set up a terminal strip.
The other for a combined one is get a small toroidal transformer and wind the secondaries, very few turns for each.
3 pin regulators 3 small bridges and three caps.
Max.
 

shteii01

Joined Feb 19, 2010
4,644
Seems like computer power supply can do that easily.

The one I am looking at has following on its label:
+5 V, 20 A
+12 V, 10 A
-5 V, 0.5 A
These meet and exceed your requirements.
 

inwo

Joined Nov 7, 2013
2,419
An example size wise is this one.
5' X 3" X 1.5"

12@2.5
24@1
5@3
-5@.5

Not quite what you need.
I would think you could find one half this size.
Maybe not. Harder to find than I first thought
 

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Thread Starter

danrulz98

Joined Sep 17, 2012
15
How come it was a 'Giant Brick' for that small a VA?
You can get wall wart types that will cover that current for <$4.00.
rig three of them up, 1-12v 2-5v with a short power bar or 4 socket surface mount outlet box, and set up a terminal strip.
The other for a combined one is get a small toroidal transformer and wind the secondaries, very few turns for each.
3 pin regulators 3 small bridges and three caps.
Max.
I'm pretty sure it's not a switch mode power supply... It weighs just over a pound.
Having 3 wallwarts like that is alright then? Even with a common ground to all of them?

And yeah, I know a computer power supply will do it, but those are quite large and expensive comparatively.
 
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