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PC power suplay modification

T

Tomislav Hajak

Jan 1, 1970
0
Hi!
I would like to know is it possible to modify pc power suplay so that I can
change voltage with pot? I hope you understand what i want, some kind of
adjustable voltage regulator with potentiometer. Anyone done something like
that? Any links?
THNX!
 
T

Tim Auton

Jan 1, 1970
0
Tomislav Hajak said:
I would like to know is it possible to modify pc power suplay so that I can
change voltage with pot?

It depends on the design of the power supply whether it's practical
but it's probably not impossible. I'm not sure how much variation you
want but ATX PSUs are designed with +3.3, +5, +12, -5 and -12V
outputs in mind so even if you could alter the output more than a
fraction of a volt it wouldn't be a good idea.
I hope you understand what i want, some kind of
adjustable voltage regulator with potentiometer. Anyone done something like
that? Any links?

Try a search for "psu voltage mod", overclockers do this kind of thing
quite a lot.

http://www.bleedinedge.com/guides/psu_3.3v_mod/psu_3.3v_mod_pg1.html

is one example.


Tim
 
J

Jeff

Jan 1, 1970
0
I have made the 3.3 V line adjustable on a ATX supply (it went something
like 2.1 to 4.5V)

The 5V line can also be modified to differnt voltages by changing the
feedback resistor (to a pot in your case). Keep in mind all the other
voltages are a ratio of the 5 V line, so you change it, you change them all.
Also keep in mind the maximum votages allowed on the capacitors, the power
good circcit, and power dissipation in various parts if you go much above
5V.

There is one link on the web where someone made a 13.8V power suppy out of
an old PC supply. He did make one mistake in assuming the transformer in the
supply was wound with wire, however he did get good results.
 
D

Dr. Anton Squeegee

Jan 1, 1970
0
Hi!
I would like to know is it possible to modify pc power suplay so that I can
change voltage with pot? I hope you understand what i want, some kind of
adjustable voltage regulator with potentiometer. Anyone done something like
that? Any links?

Possible? Maybe. Desirable? Probably not.

If you're serious about needing an adjustable bench supply, my
advice would be to build one out of something like the 'Radio Amateur's
Handbook' or buy one as surplus.

Trying to modify something like a PC's power supply, which was
designed to provide fixed voltages and currents from the ground up,
especially considering the utter lack of schematics for most of them,
would not be my first choice.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
Motorola Radio Programming & Service Available -
http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)
 
N

Nico Coesel

Jan 1, 1970
0
Jeff said:
I have made the 3.3 V line adjustable on a ATX supply (it went something
like 2.1 to 4.5V)

The 5V line can also be modified to differnt voltages by changing the
feedback resistor (to a pot in your case). Keep in mind all the other
voltages are a ratio of the 5 V line, so you change it, you change them all.
Also keep in mind the maximum votages allowed on the capacitors, the power
good circcit, and power dissipation in various parts if you go much above
5V.

There is one link on the web where someone made a 13.8V power suppy out of
an old PC supply. He did make one mistake in assuming the transformer in the
supply was wound with wire, however he did get good results.

Could you elaborate a bit more? I've made a similar modification to
get +/- 25V (50V in total) from a old PC PSU by connecting several
windings in series.
 
B

Ben Pope

Jan 1, 1970
0
Tomislav said:
Hi!
I would like to know is it possible to modify pc power suplay so that
I can change voltage with pot? I hope you understand what i want,
some kind of adjustable voltage regulator with potentiometer. Anyone
done something like that? Any links?
THNX!

What for?

The 12V and 5V lines are generally regulated with a chip and so increasing
the voltage may be hard.

Ben
 
J

Joel Kolstad

Jan 1, 1970
0
Nico Coesel said:
This one goes into the same category as gold-wiring for speakers. A
totally bogus product.

What makes you say that? Antec makes decent power supplies, and all they're
advertising is the ability to tweak the output voltage -- something the
overclockers like to do to squeeze some more performance out of their CPUs.
 
N

Nico Coesel

Jan 1, 1970
0
Joel Kolstad said:
What makes you say that? Antec makes decent power supplies, and all they're

I quote:
"Power is truly addictive"
"whopping 550 watts"
"impressive degree of control"
"Gold plated connectors."
"Voltage Feedback to maintain accurate voltage to all components: adds
stability to your system"

Sorry, but these are the labels on a bogus product. If the PMPO rating
was still being used, they would rate it at 100kW PMPO.

The specs aren't that specteculair either; PFC is not mentioned, the
efficiency is quite poor, load regulation is just within limits, it's
operating temperature is limited to 50 degrees Celcius (which is
severly low when taking into account that it has to cool itself with
an airflow in which 550 Watts got dissipated already).
I suspect this is an ordinary PC PSU (given the fact that it still has
a combined maximum output which implies one switcher / output
circuit).
 
K

Ken Taylor

Jan 1, 1970
0
Nico Coesel said:
they're

I quote:
"Power is truly addictive"

Marketing spiel.
"whopping 550 watts"

550W is 'whopping' (at least in marketing terms) in PC supplies.
"impressive degree of control"

Given the normal degree of control (~0) this is at least pretty good.
"Gold plated connectors."

Normal for connectors of any worth.
"Voltage Feedback to maintain accurate voltage to all components: adds
stability to your system"

Marketing blah blah's, but true.
Sorry, but these are the labels on a bogus product. If the PMPO rating
was still being used, they would rate it at 100kW PMPO.

The specs aren't that specteculair either; PFC is not mentioned, the
efficiency is quite poor, load regulation is just within limits, it's
operating temperature is limited to 50 degrees Celcius (which is
severly low when taking into account that it has to cool itself with
an airflow in which 550 Watts got dissipated already).
I suspect this is an ordinary PC PSU (given the fact that it still has
a combined maximum output which implies one switcher / output
circuit).

Without a CE certification, its PFC is probably shit, but then again what's
new? What's your beef with the power dissipation? At worst efficiency
quoted, it's dissipating about 250W, and it's fans will be drawing in
external air so the other 550W is irrelevant.

The product may not be up to your exacting standards, but it's harsh in the
extreme to label it 'bogus' just because the marketers are at work (as they
always are).

ken
 
T

Tim Auton

Jan 1, 1970
0
I quote:
"Power is truly addictive"
"whopping 550 watts"
"impressive degree of control"
"Gold plated connectors."
"Voltage Feedback to maintain accurate voltage to all components: adds
stability to your system"

Sorry, but these are the labels on a bogus product. If the PMPO rating
was still being used, they would rate it at 100kW PMPO.

The specs aren't that specteculair either; PFC is not mentioned, the
efficiency is quite poor

Relative to what other PC power supplies?
, load regulation is just within limits, it's
operating temperature is limited to 50 degrees Celcius (which is
severly low when taking into account that it has to cool itself with
an airflow in which 550 Watts got dissipated already).

The inefficiency of the power supply (too drunk to look it up, let's
say 75% efficiency) means that 412W was dissipated before it got to
the PSU, not 550W. PC PSU wattage is rated by consumption, not output.
It's the biggest number, that's marketing for you. Even that is making
the ridiculous assumption that the user was following the minimum ATX
spec and had only the PSU removing air from the case. The combination
of a user who actually uses the full 412W in their machine and has no
additional ventilation is so spectacularly improbable that it is
irrelevant. If the PSU is all you have removing hot air from your
components and they are using 412W you will have other problems
(overheating CPU, RAM and GFX card) well before the PSU becomes a
consideration.
I suspect this is an ordinary PC PSU (given the fact that it still has
a combined maximum output which implies one switcher / output
circuit).

It's a higher quality PSU than most of the crap out there. If you want
to compare PC PSUs the compare maximum current on the lines you are
interested in, from that you can work out the total output. I think
you'll find Antec are up there with the best in that market. PC PSUs
are cheap, mass produced items, not laboratory quality devices.

Show me a PC PSU substantially better than an Antec. If you can't then
you have found a niche in the market - go and make some and sell them.
If you're right you'll be rich.


Tim
 
M

mike

Jan 1, 1970
0
Tomislav said:
Hi!
I would like to know is it possible to modify pc power suplay so that I can
change voltage with pot? I hope you understand what i want, some kind of
adjustable voltage regulator with potentiometer. Anyone done something like
that? Any links?
THNX!

YOu'd be a lot better of to start with a real adjustable, regulated,
metered supply like one of these:
http://nm7u.tripod.com/homepage/te.html
mike

--
Bunch of stuff For Sale and Wanted at the link below.
laptops and parts Test Equipment
Honda CB-125S
TEK Sampling Sweep Plugin and RM564
Tek 2465 $800, ham radio, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/
 
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