old ATX power supply needed for science project

J

John B

Guest
We've got a very old Dell computer, of the '486 vintage. The power supply
resembles that seen used with countless ATX form-factor motherboards. My
son can use the +5 and +/- 12 volts for his science project.

There is a 20-contact connector that plugs into the mobo. I presume that if
a certain pair of those wires is shorted, the power supply will turn on.
Anyone know how to make such a power supply perform, in a stand-alone
position? No mobo will be available.

Thanks.
 
"John B" <jb@nospam.com> wrote in message
news:ilfce.26497$c42.24816@fe07.lga...
There is a 20-contact connector that plugs into the mobo. I presume that
if
a certain pair of those wires is shorted, the power supply will turn on.
Anyone know how to make such a power supply perform, in a stand-alone
position? No mobo will be available.
Click to expand...
Bring nPS_ON low. In other words, tie the green wire to one of the black
wires.

See http://pinouts.ru/data/atxpower_pinout.shtml for the pinout.

Jonathan
http://cq.cx/
 
This pertains to generic ATX.
http://www.duxcw.com/faq/ps/ps1.htm
shows that pins 14 and 15 should be shorted.
The colors correspond to an ATX power supply I have in a "clone" computer.

Dell is different, though.
http://pinouts.ru/data/dell_atxpower_pinout.shtml
looks right, based on wire colors.

I presume I short the grey wire to a black wire, to turn the thing on.
Any advice appreciated.
 
Thanks! I just found the same website. The Dell ATX disagrees with the
generic ATX, though. Dell has proprietary pinouts.
The grey wire must go low.

"Jonathan Westhues" <please-see-website@nospam.com> wrote in message
news:aHfce.11901$BW6.1071701@news20.bellglobal.com...
"John B" <jb@nospam.com> wrote in message
news:ilfce.26497$c42.24816@fe07.lga...
There is a 20-contact connector that plugs into the mobo. I presume
that
if
a certain pair of those wires is shorted, the power supply will turn on.
Anyone know how to make such a power supply perform, in a stand-alone
position? No mobo will be available.

Bring nPS_ON low. In other words, tie the green wire to one of the black
wires.

See http://pinouts.ru/data/atxpower_pinout.shtml for the pinout.

Jonathan
http://cq.cx/
Click to expand...
 
"John B" <jb@nospam.com> wrote in message
news:l5gce.26203$Ow2.8007@fe06.lga...
Dell is different, though.
http://pinouts.ru/data/dell_atxpower_pinout.shtml
looks right, based on wire colors.

I presume I short the grey wire to a black wire, to turn the thing on.
Any advice appreciated.
Click to expand...
How strange; I thought that was standard. But I would say yes then, grey to
black.

Jonathan
http://cq.cx/
 
Actually, if I am to interpret the diagram for the Dell pinouts literally,
the PS_On (grey wire) should be tied high (+5?) to turn the power supply on.
Yeah, but that doesn't make a lot of sense, unless that very line is
considered to be "low" when open... Well, I suppose anything is possible,
but I will be that a tie to ground will turn the thing on. That would imply
that a correction is in order for that diagram.

The same website made a point if declaring the green wire to be "true low"
by naming it "/PS_ON." So I guess I'll have to experiment.

"John B" <jb@nospam.com> wrote Dell has proprietary pinouts.
The grey wire must go low.
Click to expand...
 
I shorted grey to black, and nothing happened. I was hoping the cooling fan
would turn on. I then shorted grey to other colored wires, and still no
action. The computer from which this old p/s was pulled was not dead...just
obsolete. So the p/s is supposed to be OK.
Tomorrow my son will pull the p/s out of another old Dell. He'll try the
same thing. But this will have to wait until tomorrow.
The p/s we tried has a fuse deep inside, and not the kind you can see
through. So I unplugged the power cord from the wall receptacle, shorted
the power prongs to dissipate any residual charge, and rang the 117VAC
prongs with an ohmmeter. There was some conductance...implying that the
fuse is OK.
Mańana.

"Jonathan Westhues" <please-see-website@nospam.com> wrote in message
news:uhgce.12286$BW6.1079634@news20.bellglobal.com...
"John B" <jb@nospam.com> wrote in message
news:l5gce.26203$Ow2.8007@fe06.lga...
Dell is different, though.
http://pinouts.ru/data/dell_atxpower_pinout.shtml
looks right, based on wire colors.

I presume I short the grey wire to a black wire, to turn the thing on.
Any advice appreciated.

How strange; I thought that was standard. But I would say yes then, grey
to
black.

Jonathan
http://cq.cx/
Click to expand...
 
"John B" <jb@nospam.com> wrote in message
news:aVgce.26384$Jg7.7811@fe03.lga...
I shorted grey to black, and nothing happened. I was hoping the cooling
fan
would turn on. I then shorted grey to other colored wires, and still no
action. The computer from which this old p/s was pulled was not
dead...just
obsolete. So the p/s is supposed to be OK.
Tomorrow my son will pull the p/s out of another old Dell. He'll try the
same thing. But this will have to wait until tomorrow.
The p/s we tried has a fuse deep inside, and not the kind you can see
through. So I unplugged the power cord from the wall receptacle, shorted
the power prongs to dissipate any residual charge, and rang the 117VAC
prongs with an ohmmeter. There was some conductance...implying that the
fuse is OK.
Click to expand...
You might try measuring the voltage between the +5VSB line (pin 6 with the
strange Dell layout) and ground. It should be about 5 V, even when the power
supply is "off".

Jonathan
http://cq.cx/
 
There is some more info here
http://answers.google.com/answers/threadview?id=52126 that corroborates the
theory that the grey wire should be shorted to ground.
So I shorted the grey wire to the chassis, just in case that's different
from the black wire. The fan did not start up.
I put a DC voltmeter between red and black, hoping to see 5 VDC. When I
shorted the grey wire to the can, I noticed a very brief blip between red
and black. That implies that the p/s is folding back, after briefly
supplying +5, perhaps as a consequence of the zero load at the various
voltage supply lines. There is no motherboard here.
I shorted grey to chassis again, this time monitoring for +12 VDC. Same
thing; momentary blip on the voltmeter.
So I think there is some foldback issue, here, in the p/s design.

"Jonathan Westhues" <please-see-website@nospam.com> wrote
You might try measuring the voltage between the +5VSB line (pin 6 with the
strange Dell layout) and ground. It should be about 5 V, even when the
power
supply is "off".

Jonathan
http://cq.cx/
Click to expand...
 
"John B" <jb@nospam.com> wrote in message
news:l5gce.26203$Ow2.8007@fe06.lga...
This pertains to generic ATX.
http://www.duxcw.com/faq/ps/ps1.htm
shows that pins 14 and 15 should be shorted.
The colors correspond to an ATX power supply I have in a "clone" computer.

Dell is different, though.
http://pinouts.ru/data/dell_atxpower_pinout.shtml
looks right, based on wire colors.

I presume I short the grey wire to a black wire, to turn the thing on.
Any advice appreciated.
Click to expand...
The black wires are Ground anything Yellow, Red or Orange
will be supply, Any other colors may be for switching.
 
"John B" <jb@nospam.com> wrote in message
news:fdice.26539$c42.16336@fe07.lga...
I put a DC voltmeter between red and black, hoping to see 5 VDC. When I
shorted the grey wire to the can, I noticed a very brief blip between red
and black. That implies that the p/s is folding back, after briefly
supplying +5, perhaps as a consequence of the zero load at the various
voltage supply lines. There is no motherboard here.
I shorted grey to chassis again, this time monitoring for +12 VDC. Same
thing; momentary blip on the voltmeter.
So I think there is some foldback issue, here, in the p/s design.
Click to expand...
Wait, you don't have any load? A lot of them will run (with bad regulation)
with no load but they aren't designed to. Can you connect an old disk drive
or something, or a light bulb or a power resistor across the 5 V rail?

Did you measure the +5VSB line to make sure that the power supply is powered
and kind of working?

Jonathan
http://cq.cx/
 
Yeah. There was nothing at +5VSB.
I like you're idea of powering an old disc drive. I've got lots of junk
like that. I just don't want to connect the motherboard from the
cannibalized computer, if I can help it.
So you agree...that "no load" equals "no go"?
I wonder what the reason for that would be? I suppose the gods of mobo
design have some reason for this.
Like Tevya said in "Fiddler on the Roof," would it upset some great eternal
plan, if I were to know... WHY?!

"Jonathan Westhues" <please-see-website@nospam.com> wrote in message
news:9nice.12361$BW6.1126517@news20.bellglobal.com...
"John B" <jb@nospam.com> wrote in message
news:fdice.26539$c42.16336@fe07.lga...
I put a DC voltmeter between red and black, hoping to see 5 VDC. When I
shorted the grey wire to the can, I noticed a very brief blip between
red
and black. That implies that the p/s is folding back, after briefly
supplying +5, perhaps as a consequence of the zero load at the various
voltage supply lines. There is no motherboard here.
I shorted grey to chassis again, this time monitoring for +12 VDC. Same
thing; momentary blip on the voltmeter.
So I think there is some foldback issue, here, in the p/s design.

Wait, you don't have any load? A lot of them will run (with bad
regulation)
with no load but they aren't designed to. Can you connect an old disk
drive
or something, or a light bulb or a power resistor across the 5 V rail?

Did you measure the +5VSB line to make sure that the power supply is
powered
and kind of working?

Jonathan
http://cq.cx/
Click to expand...
 
"John B" <jb@nospam.com> wrote in message
news:f%ice.26562$Jg7.3532@fe03.lga...
Yeah. There was nothing at +5VSB.
I like you're idea of powering an old disc drive. I've got lots of junk
like that. I just don't want to connect the motherboard from the
cannibalized computer, if I can help it.
So you agree...that "no load" equals "no go"?
Click to expand...
It might work with no load or it might not, but if it works at all then it
will work with a load. Hook up an old hard drive or something and you will
be sure.

If you check to make sure that the +5VSB voltage is present before you short
any wires together then you can at least be sure that you have the pinout
right.

I wonder what the reason for that would be? I suppose the gods of mobo
design have some reason for this.
Like Tevya said in "Fiddler on the Roof," would it upset some great
eternal
plan, if I were to know... WHY?!
Click to expand...
Computer power supplies are switchmode power supplies. They transfer energy
from a high voltage DC rail (generated directly off the mains voltage) into
the load voltages in short pulses. The power supply can only put energy into
the load; with no load there is nothing consuming energy, and it is
difficult to control the output voltage so it shuts down.

Jonathan
http://cq.cx/
 
On Thu, 28 Apr 2005 21:47:01 -0700, "John B" <jb@nospam.com> wrote:

Yeah. There was nothing at +5VSB.
I like you're idea of powering an old disc drive. I've got lots of junk
like that. I just don't want to connect the motherboard from the
cannibalized computer, if I can help it.
So you agree...that "no load" equals "no go"?
I wonder what the reason for that would be? I suppose the gods of mobo
design have some reason for this.
Like Tevya said in "Fiddler on the Roof," would it upset some great eternal
plan, if I were to know... WHY?!
Click to expand...
No-load operation is an added expense, not justified in the original
application. These units were/are extremely cost-critical.

Some units may even overshoot - triggering an overvoltage protection
circuit. Reseting this may require removal of input power for some
minutes.

RL
 
On Thu, 28 Apr 2005 18:28:32 -0700, John B wrote:

This pertains to generic ATX.
http://www.duxcw.com/faq/ps/ps1.htm
shows that pins 14 and 15 should be shorted.
The colors correspond to an ATX power supply I have in a "clone" computer.

Dell is different, though.
http://pinouts.ru/data/dell_atxpower_pinout.shtml
looks right, based on wire colors.

I presume I short the grey wire to a black wire, to turn the thing on.
Any advice appreciated.
Click to expand...
This PSU should not even be designated ATX. It doesn't conform to ATX
pinouts. While I've never purchased an assembled system you can sure bet
I'll never purcahse a Dell after seeing this.

--
Abit KT7-Raid (KT133) Tbred B core CPU @2400MHz (24x100FSB)
My server http://wesnewell.no-ip.com/cpu.php
Verizon server http://mysite.verizon.net/res0exft/cpu.htm
 
do not switch them on without a load
or dummy load.

"John B" <jb@nospam.com> wrote in message
news:ilfce.26497$c42.24816@fe07.lga...
We've got a very old Dell computer, of the '486 vintage. The power supply
resembles that seen used with countless ATX form-factor motherboards. My
son can use the +5 and +/- 12 volts for his science project.

There is a 20-contact connector that plugs into the mobo. I presume that
if
a certain pair of those wires is shorted, the power supply will turn on.
Anyone know how to make such a power supply perform, in a stand-alone
position? No mobo will be available.

Thanks.
Click to expand...
 
I understand your indignation, where Dell has "hijacked" the term ATX while
imposing a proprietary wiring specification. HOWEVER. Dell has been making
fabulous computers for many years, offers good warranties, and has many
trampled competitors, not to mention loyal repeat customers, to prove its
suporiority in the marketplace.

Although I build my own, as do you, most people don't any do that more than
they build their own cars. And I have been in too many noname computer
"factories" where simple anti-static rules are ignored. That compares to
medical practices that ignore anti-biotic precautions. Of course, testing
was virtually non-existent.

Years ago, I compared Dell to Gateway. Gateway was cheaper, but admitted to
testing only one in five computers coming off the line. Dell tested every
one.

"Wes Newell" <w.newell@TAKEOUTverizon.net> wrote >
This PSU should not even be designated ATX. It doesn't conform to ATX
pinouts. While I've never purchased an assembled system you can sure bet
I'll never purcahse a Dell after seeing this.

--
Abit KT7-Raid (KT133) Tbred B core CPU @2400MHz (24x100FSB)
My server http://wesnewell.no-ip.com/cpu.php
Verizon server http://mysite.verizon.net/res0exft/cpu.htm
Click to expand...
 
The power supply works. It needs a load, such as an old floppy drive. I
used an old 5 1/4" floppy drive.
Interestingly, the load must exist BEFORE the grey wire is shorted to ground
AND (in the Boolean sense) the 117VAC line is plugged in. IOW, either of
the two latter conditions can be used to turn the p/s on or off.
Furthermore, the load status is latched by the p/s, at the moment the p/s is
turned on. IOW, I can disconnect the load after powering up the p/s, and
voltages remain on the colored wires. I notice, however, that the +12
(yellow) degrades on my DVM when the load is disconnected.
Simply stated, load status is latched at the moment the grey wire is
grounded and the 117VAC is present.

It was not sufficient to place a mere 150 ohm resistor between +5V and GND.
The floppy drive sufficed.

The power OK line was +5 only when voltages are available at p/s outputs.
Furthermore, the cooling fan turns on under the same condition. So the
power OK line and cooling fan are equal indicators.

Thanks for your help.
My son will be delighted.

"Jonathan Westhues" <please-see-website@nospam.com> wrote
It might work with no load or it might not, but if it works at all then it
will work with a load. Hook up an old hard drive or something and you will
be sure.

If you check to make sure that the +5VSB voltage is present before you
short
any wires together then you can at least be sure that you have the pinout
right.

Computer power supplies are switchmode power supplies. They transfer
energy
from a high voltage DC rail (generated directly off the mains voltage)
into
the load voltages in short pulses. The power supply can only put energy
into
the load; with no load there is nothing consuming energy, and it is
difficult to control the output voltage so it shuts down.

Jonathan
http://cq.cx/
Click to expand...
 
From the way I see it, Gateway committed suicide by opening
"dedicated" showroom stores. Dell lives because they provide a
competitive product (nothing special) and don't have showrooms or
distributor shelves to stock with equipment that is soon antiquated -
at least price wise. With this model, Dell has much lower business
cost overhead.

Forrest

Motherboard Help By HAL web site:
http://home.comcast.net/~mobo.help/


On Fri, 29 Apr 2005 06:34:00 -0700, "John B" <jb@nospam.com> wrote:

< snip >
Years ago, I compared Dell to Gateway. Gateway was cheaper, but admitted to
testing only one in five computers coming off the line. Dell tested every
one.

snip
Click to expand...
 
I have an idea that Dell was better capitalized, too. IOW, investors were
more willing to plunge dollars into Dell than Gateway. So how did Dell earn
that enviable status, many years ago? By relentlessly earning customer
loyalty. By leading the field in "mail order" marketing. Dell has always
had a sensational catalog, and a fabulous website. And though Dell was
typically a bit more expensive than Gateway, its customers swore the
difference was worth the cost.

"- HAL9000" <gumpy@mail.org> wrote in message
news:2su471d48t4v9pm9ogg2su4vmn8s4081sa@4ax.com...
From the way I see it, Gateway committed suicide by opening
"dedicated" showroom stores. Dell lives because they provide a
competitive product (nothing special) and don't have showrooms or
distributor shelves to stock with equipment that is soon antiquated -
at least price wise. With this model, Dell has much lower business
cost overhead.

Forrest

Motherboard Help By HAL web site:
http://home.comcast.net/~mobo.help/


On Fri, 29 Apr 2005 06:34:00 -0700, "John B" <jb@nospam.com> wrote:

snip

Years ago, I compared Dell to Gateway. Gateway was cheaper, but admitted
to
testing only one in five computers coming off the line. Dell tested
every
one.

snip
Click to expand...
 
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