[sdiy] BIG PSU ISSUES

[Dave Manley]

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