On Oct 2, 11:37*am, wrote:
On Oct 2, 4:29*am, raypsi wrote:





On Oct 1, 12:55*pm, terry wrote:

We recently modified such a power supply to get a single 12 volt DC
output at about 20 amps for a particular, amateur radio application.
In order to do so we had to load one of the 5 volt outputs with a
couple of amps in order to get the unit to work; but that's normal.

Hey terry

I did that very same thing loaded the 5volt with 5ohm at 5 watt.
Ran my TenTec 526 off the 12 volt side of the PC power supply.
I thought it was the sweetest thing since sliced bread. Then
people started telling me I had this strange background noise.
They asked me what was going on in my shack. I had this strange
eerie noise in my shack, so they thought. Wasn't in my shack per
say but it was the PC power supply. Nobody knew I was running
a PC supply to power my rig.

73 OM

n7zu

I also use a modified PC power supply with no problems. I did add a
filter removed
from a commercial computer SMPS. I don't know the values of the
components but its a Pi filter
and the inductor is wound on what looks like a ferrite rod. The caps
are some pretty big disk
that had the writing rubbed off of them a long time ago. As Grumpy put
it. I like to "Frankenstien"
some of my projects.

I have been giving some thought as to what it would take to modify a
PC power supply for HV use.
I have been thinking along two lines,

1 Connect a second step-up transformer before the rectifiers.
2 Replace the transformer with one with a HV winding putting a 5volt
winding on the new
transformer for loading and feedback.

Jimmie- Hide quoted text -

- Show quoted text -

Great info: Thanks for all the ideas and especially about the warning
that the HV would be on the line side (input) from115/230 volt mains.
Unless a 60 hertz full isolation transformer were used; the weight and
size of which sort of negates the idea of using a lighter weight SPS!

I too used to fix TVs without power transformers, using selenium
rectifiers (boy could they stink!) and voltage doubler circuits to
provide B+. That was back in the mid late 1950s. I also made up a
little B+ power supply in a box clipped in during house calls to show
a customer that the problem was indeed inside the chassis and it had
to be taken away for a 'bench job'!

By that and means of never charging for a house call if I didn't fix
the set in situ; built up a reputation for straightforward dealing
which, despite the slightly funny accent of a British immigrant to
Canada, some 15 years later, may have helped me become elected to the
areas first town council? And that in a day and age when TV repairmen
didn't have the best reputation in the world (well at least around
here) for ethical dealings!

These days customers are a lot more cynical and questioning; and
rightly so!

BTW first heard about SPS in the telephone industry, before PC were
common; when power supplier representatives started telling us about
'rectifier/power supplies' that had efficiencies of over 80%.