Re: Can a power supply have too much current?

[Don Bruder <dakidd@sonic.net>]

In article <45e61141$0$91139$c30e37c6@lon-reader.news.telstra.net>,
 Tristan Mumford <xtristan.xmumford@xgmail.xcom> wrote:

> G'day!
> 
> I just received my IIgs. I am absolutely ecstatic!
> However there is one minor issue. As its origins are in the US it means it
> has a 110v supply.
> This prompted me to go to the altar of Ancient and Rusty Things in the
> backyard to have a scavenge.
> I found a weird looking supply of unknown origin. It's a long thin beastie
> like a lot of compact computers have. The difference is it has three
> connectors.
> There's the 0 and +5v connector, which has two 0v, then two +5 lines. They
> look to plug into some kind of blade connector. Very thick wires. Then
> theres a tiny one with jumper style female connectors that supplies other
> voltages. The third is a drive supply connector.
> 
> Anyway, IIRC the +5v is roughly 15A, the 12v is roughly 5A. Usually I'm
> happy about having more current. However the difference here makes me more
> than a little nervous.
> 
> Any feedback would be appreciated.
> 
> Tristan.

If it's a regulated supply (Which pretty much all computer power 
supplies are) then it's a non-issue. Unregulated supplies can be dicey - 
draw too little current (amps) from them, and the voltage can go 
sky-high - An unregulated 15 amps @ 5 volts supply might go as high as 
12-15 volts in certain low-draw situations. Likewise, drawing too much 
from it might cause the voltage to drop to some ridiculously low number.

The amp rating of a power supply isn't "I'm going to shove 15 amps at 5 
volts down the wire", it's "I can handle feeding up to 15 amps at 5 
volts if that's what the stuff you hook up to me requires - but any more 
than that, and all my "magic smoke" might leak out". 

In other words, as long as "+5" is actually "+5", regardless of the load 
(and the same "+12 is +12" for the 12 volt side of things) and the power 
supply ratin says it can offer *AT LEAST* the required amps, then you're 
good to go.

-- 
Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist,
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