Its both, the regulator chip monitors both the 12V and 5 volt output.
They can be easily modified to monitor just one voltage or to change
the output voltage somewhat.
By changing the value of a resistor you can "fool" the regulator into
"thinking" its putting out more or less voltage than it really is
thereby increase / decrease the output voltage.
he's not talking about LOAD resistors,but the resistive divider inside the
PS that sets the output voltage.
But changing the output V of one of the output voltages will also change
some of the other unregulated supplies. The supplies track each
other,unless they have a separate regulator circuit.
I have a stack of old PC supplies and most of them will power up and
be stable with nothing plugged into them. I know the old AT supply
needed a load but the newer ones must have some internal load to
On Mar 8, 9:15 pm, email@example.com (Don Klipstein) wrote:
Regulation depends on the quality of the transformer. On a lot of
cheap import transformers a 12 volt transformer may put out 18 volts
into a light load then drop to 10 when pushed to near there rated
capacity. Get a good transformer and you dont have to worry about
this. Good transformers arent cheap but neither is replacing cheap
ones. My 12.6 volt 10 amp Stancor transformer only varies about 1 volt
from no load to full output.
Besides quality, there are 2 other factors:
1. Voltage variation with change of load tends to be less with larger
transformers and more with smaller ones. Though my experience is that
upsizing the transformer tends to make load voltage more excessive, until
the transformer gets so big that open circuit voltage is only a little
higher than the nominal load voltage. A 12.6V 10 amp Stancor brand one is
a big as well as decent quality transformer as far as ones to find inside a
home go - though maybe only mildly oversized for 60 watts worth of halogen
lights, probably not especially bad for this job after all.
(If voltage runs half a volt high at 5 or slightly more amps, then 60
watts worth of halogen lamps will be supplied 13.1 volts. If the lamps
get that much voltage after wiring voltage drops, expect
incandescent/halogen lamps rated for 12 volts even to have life expectancy
reduced maybe 60%.)
2. Most wallwarts have DC output, and not only the transformer windings
but also the rectifier circuit (diodes and filter capacitor) has issues of
load voltage varying with load current.
- Don Klipstein ( firstname.lastname@example.org)
The origonal power supply was too small. 57 watts power supply for 60
watt load? You need a 90 watt power supply or larger. If ther is no
watt rating on the replacement I would look for 8 amps or better.
(Amazon.com product link shortened)
Remember, the track lights are 12 volts AC, not DC. Running them on DC
will work, but the wiring of the lights may not be designed for DC.
Probably it's cheaper to buy another set of lights from Ikea and use the
transformer from it.
You can buy a transformer at a place like
Maybe Home Depot or Lowe's sells them as well.
In the olden days you could buy a 12.6V filament transformer for a few
bucks, but no more.
Again, it's a bad idea to buy a 110VAC to 12VDC power adapter for track
Actually the wiring will make no difference - and as long as you are
switching the high voltage (ac) you don't need to warry about DC rated
The lamps will "like" regulated DC better than sloppy AC too.
And have the same cheap crap fail in the same manner in the same short
What's wrong with this picture???
It's a waste of money if it costs you more than an adequate AC
transformer - but even a GOOD NEW ATX power supply of adequate
capacity can be bought for under $30 - used PC/AT supplies are a dime
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