[RndTbl] partial PS use?

[Wyatt Zacharias]

Do the resistors have their power rating on them? 1.6A at 12V is 19.2 watts
total. You'll need some hefty resistors to sink that much power into.

Out of curiosity, how much power do you actually need from the 5V rail?
Single voltage switch mode power supplies can be had for under $50 with
decent amperage ratings.

--
Wyatt Zacharias


On Wed, Feb 17, 2016 at 11:54 AM, Trevor Cordes <trevor at tecnopolis.ca>
wrote:

> On 2016-02-15 Hartmut W Sager wrote:
> > The -5V and -12V are probably fine with no load, but the +12V line
> > should have at least the minimum required load (whatever that might
> > be).  Just use a suitable power resistor (power resistor means it
> > won't fry into a molten lump) on the +12V line.  In the absence of
> > info on the PS label, I'd go for loading the +12V line with about 10%
> > of its maximum power/amps.  Use V = IR and P = IV to do the algebra
> > to get the right resistance (ohms).
>
> Thanks for the tip!  The old PS indeed says a minimum on the +12V of
> 1.3A.  I paralleled 2 15ohm power resistors (5%; the big huge white
> rectangle ones) to approximate a 1.3A or higher (1.6 actually) load.  I
> only had a limited selection of power resistors around here.
>
> I can get the whole unit to power on now, and seems to try to boot and
> blink some LEDs, yay!
>
> BUT the power resistors get REAL hot REAL fast.  Like too hot to touch
> in under 30s.  Does that sound right?  Not sure I can deliver that to
> customer like that.  Any other ideas?  Different resistors?  Maybe try
> a "real" load, but what?
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