"Dave Plowman (News)" wrote in message
...
In article ,
Adrian C wrote:
Arfa Daily wrote:

Jacking these PSUs up a couple of volts is not usually that hard.
There's often an 'adjustable zener' IC on the primary side, which is
fed from the secondary side via an opto coupler. This zener serves as
the reference to set the PWM for the desired output voltage. Altering
that voltage is just a case of changing one resistor to alter the
reference voltage.


Another resource.

http://www.pavouk.org/hw/en_atxps.html

The above schematic could be frigged about with by selecting a new value
for R25.

Typical 13.8v project.

http://www.webx.dk/oz2cpu/radios/psu-pc1.htm

The one I have to hand is a bit more modern and uses an all in one SG6105
supervisor IC.

--
*Acupuncture is a jab well done*

Dave Plowman London SW
To e-mail, change noise into sound.

There are reference and feedback inputs at pins 11,12,13 &14 on that IC, and
if you examine the internal schematics, you will see that behind those pins
are the 'adjustable zeners' which are often external devices on PSUs which
use a slightly less sophisticated management IC. I expect that if you played
with the resistors attached to those pins, you could alter the output
voltage of the supply. One thing to note is that this IC also has under and
over-voltage lockouts, and if the feature has been implemented on your PSU,
then cranking the 12v up to 13.8v, may result in an unwanted shutdown, so
you might need to disable this feature.

Just as a matter of interest, what are you hoping to run from this PSU ?
Requiring 13.8v would suggest that it is something designed for mobile use.
However, most such devices will happily run from 12v, as this may be all the
vehicle voltage that's available, if the engine isn't running.

Arfa