[sdiy] BIG PSU ISSUES

[Dave Manley]

That should be fine.  You need to measure the current and see what your 
load is drawing, you could have a significant drop across those 22 ohm 
resistors (22 ohms * 50 mA = 1.1V).  Also if the supply is new to you, 
put a resistive load on it and see if it works properly - ie can it 
deliver the rated current at the rated voltage.

-Dave

Dan Snazelle wrote:
> i am using 22 gauge solid core wires.
> 
> 
> is that too big/small??
> 
> 
> thanks
> 
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>  > Date: Wed, 13 Aug 2008 15:24:59 -0700
>  > From: dlmanley at sonic.net
>  > CC: synth-diy at dropmix.xs4all.nl
>  > Subject: Re: [sdiy] BIG PSU ISSUES
>  >
>  > Dan Snazelle wrote:
>  > > I have a nice powerone supply. its a 12volt or 15 volt +/- volt. I 
> am running it at 12 volts and without a load i used the trimmers to set 
> it for 12volts.
>  > >
>  > > i think this model can handle at least .5 amps per channel. i think 
> actually .75 (in +15/-15 mode it handles less amperage)
>  > >
>  > > now when i hook up my current project, which is three giant 
> breadboards (of mainly CMOS low draw chips) to my STAR breadboard (which 
> is the PSU hooked up to a breadboard which everything else plugs into 
> with 22r resistors as fuses), and i take a reading of the VOLTS of my 
> project i get a reading of 9 volts.
>  > >
>  > > My questions
>  > >
>  > > 1. there are trimmers on the PSU to push it back up to almost 12 
> volts post load..should i do this? or are the trimmers only for PRE LOAD?
>  > > 2. how can i get around this? could my PSU be messed up?
>  > >
>  > > 3. i know these are low amp chips. i only have ONE led on the 
> entire project. there are some opamps.
>  > > is load voltage not the same? do i not need to worry? or should i 
> get a measured 12 volts? and -12 volts?
>  > >
>  > >
>  > > thanks so much
>  > >
>  >
>  > What is the current with the load attached (or if you can't measure
>  > current, as someone else asked, what's the voltage drop across the 22
>  > ohm resistors).
>  >
>  > If you put a resistive load (of proper wattage!) on the supply does the
>  > supply work to spec? The supply could be defective.
>  >
>  > Perhaps a silly reply in this case, but what gauge wires are you using
>  > to hook the supply to the load? I saw someone once blame a supply for
>  > low voltage at the load, and then I asked him why his power wires were
>  > warm to the touch! I guess if the insulation was dripping off, or the
>  > wires started smoking he would have eventually figured it out. See if
>  > there is a voltage drop across the power wires.
>  >
>  > -Dave
>  >
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