How make UNconnected PC power supply operate?
 

For testing purposes, I'd like to make an PC power supply operate when
NOT installed in a PC. I've heard that the AT supply needs at least
SOME load on its 5-volt output before it will operate; is an ampere
or two sufficient?

For ATX supplies, I visited a friendly computer-repair store today and
examined the "cheater" into which they plugged UNconnected ATX supplies;
it had three pairs of connections:
1) A jumper from Ground to PS-ON
2) an LED and resistor from PowerOK to Ground
3) two wires from +5V and ground going into something about the size
of a small box of matches which was shrink-wrapped to the cable

They wouldn't let me disassemble it !-)
Was there probably a 5-ohm resistor in that box?
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

wrote in message ...
For testing purposes, I'd like to make an PC power supply operate when
NOT installed in a PC. I've heard that the AT supply needs at least
SOME load on its 5-volt output before it will operate; is an ampere
or two sufficient?

For ATX supplies, I visited a friendly computer-repair store today and
examined the "cheater" into which they plugged UNconnected ATX supplies;
it had three pairs of connections:
1) A jumper from Ground to PS-ON
2) an LED and resistor from PowerOK to Ground
3) two wires from +5V and ground going into something about the size
of a small box of matches which was shrink-wrapped to the cable

They wouldn't let me disassemble it !-)
Was there probably a 5-ohm resistor in that box?

Most all computer switching supplies need some load on it to start. About
1/2 to 1 amp should be fine. YOu can use a 5 ohm resistor rated at 10 watts
or so to put a load on the 5 volt line. When testing an AT supply I usually
just hook up to an old hard drive.
If you have some kind of load already hooked to the supply they you can
forget the resistor load.

Using PC power supply for powering other circuits than PC
PC power supplies are specifically designed for PC electronics.
Typically they work well in the current range a typical PC takes. If you
take too low current form the ouputs, the power supply myght not work
properly. If you load only one output, you might run into troubles of
poor regulation. Typically PC power supplies regulate the output voltage
of all outputs according the voltage in 5V output pin. If you don't put
enough load to +5V output, you don't get stable +12V output from the
power suppply.

I found the above, on the web, hope it helps...

Warmest regards,
John

wrote in message ...
For testing purposes, I'd like to make an PC power supply operate when
NOT installed in a PC. I've heard that the AT supply needs at least
SOME load on its 5-volt output before it will operate; is an ampere
or two sufficient?

For ATX supplies, I visited a friendly computer-repair store today and
examined the "cheater" into which they plugged UNconnected ATX
supplies;
it had three pairs of connections:
1) A jumper from Ground to PS-ON
2) an LED and resistor from PowerOK to Ground
3) two wires from +5V and ground going into something about the size
of a small box of matches which was shrink-wrapped to the cable

They wouldn't let me disassemble it !-)
Was there probably a 5-ohm resistor in that box?
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and
cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785)
539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle,
Pistol)

On 1 Jun 2005 17:16:26 -0500, wrote:

For testing purposes, I'd like to make an PC power supply operate when
NOT installed in a PC. I've heard that the AT supply needs at least
SOME load on its 5-volt output before it will operate; is an ampere
or two sufficient?

For ATX supplies, I visited a friendly computer-repair store today and
examined the "cheater" into which they plugged UNconnected ATX supplies;
it had three pairs of connections:
1) A jumper from Ground to PS-ON
2) an LED and resistor from PowerOK to Ground
3) two wires from +5V and ground going into something about the size
of a small box of matches which was shrink-wrapped to the cable

They wouldn't let me disassemble it !-)
Was there probably a 5-ohm resistor in that box?

I recall about a year or so ago, one of the ham magazines had an
article about converting PC power supplies for use as a radio PS.

Might be CQ or QST. The article gave specs on what youe are looking
for, but I do not remember details. If you are an ARRL member, you can
do a search on past QST articles on their website.

Happy trails,
Gary (net.yogi.bear)
--
At the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

On 1 Jun 2005 17:16:26 -0500, wrote:

For testing purposes, I'd like to make an PC power supply operate when
NOT installed in a PC. I've heard that the AT supply needs at least
SOME load on its 5-volt output before it will operate; is an ampere
or two sufficient?

For ATX supplies, I visited a friendly computer-repair store today and
examined the "cheater" into which they plugged UNconnected ATX supplies;
it had three pairs of connections:
1) A jumper from Ground to PS-ON
2) an LED and resistor from PowerOK to Ground
3) two wires from +5V and ground going into something about the size
of a small box of matches which was shrink-wrapped to the cable

They wouldn't let me disassemble it !-)
Was there probably a 5-ohm resistor in that box?

Hi Myron, how's the new QTH going?

Plug in an old HD. It should provide enough of a load to get the PS
started and regulating.

Russ - kf4wxd

"Russ" wrote in message
...
On 1 Jun 2005 17:16:26 -0500, wrote:

For testing purposes, I'd like to make an PC power supply operate when
NOT installed in a PC. I've heard that the AT supply needs at least
SOME load on its 5-volt output before it will operate; is an ampere
or two sufficient?

For ATX supplies, I visited a friendly computer-repair store today and
examined the "cheater" into which they plugged UNconnected ATX supplies;
it had three pairs of connections:
1) A jumper from Ground to PS-ON
2) an LED and resistor from PowerOK to Ground
3) two wires from +5V and ground going into something about the size
of a small box of matches which was shrink-wrapped to the cable

They wouldn't let me disassemble it !-)
Was there probably a 5-ohm resistor in that box?

Hi Myron, how's the new QTH going?

Plug in an old HD. It should provide enough of a load to get the PS
started and regulating.

Russ - kf4wxd

This link is a good one for using PC power supplies. It
works great. I did it.

Charles, ka8jvx

http://antennex.com/preview/archive3/powers.htm

Yes, that is a good link, August has lot of good info.

Be sure to discharge any capacitors inside the cage
on any switching supply, the voltages inside the cage
are LETHAL !!!

ceh:

that is a good URL... I forgot to mention about some (a lot) of
supplies needing the "power good" signal before they even function...

Warmest regards,
John

"ceh" wrote in message
...

"Russ" wrote in message
...
On 1 Jun 2005 17:16:26 -0500, wrote:

For testing purposes, I'd like to make an PC power supply operate
when
NOT installed in a PC. I've heard that the AT supply needs at least
SOME load on its 5-volt output before it will operate; is an ampere
or two sufficient?

For ATX supplies, I visited a friendly computer-repair store today
and
examined the "cheater" into which they plugged UNconnected ATX
supplies;
it had three pairs of connections:
1) A jumper from Ground to PS-ON
2) an LED and resistor from PowerOK to Ground
3) two wires from +5V and ground going into something about the
size
of a small box of matches which was shrink-wrapped to the cable

They wouldn't let me disassemble it !-)
Was there probably a 5-ohm resistor in that box?

Hi Myron, how's the new QTH going?

Plug in an old HD. It should provide enough of a load to get the PS
started and regulating.

Russ - kf4wxd

This link is a good one for using PC power supplies. It
works great. I did it.

Charles, ka8jvx

http://antennex.com/preview/archive3/powers.htm

"John Smith" ) writes:
ceh:

that is a good URL... I forgot to mention about some (a lot) of
supplies needing the "power good" signal before they even function...

Warmest regards,
John

No, the "power good" is an output from the power supply.

Michael VE2BVW

"ceh" wrote in message
...

"Russ" wrote in message
...
On 1 Jun 2005 17:16:26 -0500, wrote:

For testing purposes, I'd like to make an PC power supply operate
when
NOT installed in a PC. I've heard that the AT supply needs at least
SOME load on its 5-volt output before it will operate; is an ampere
or two sufficient?

For ATX supplies, I visited a friendly computer-repair store today
and
examined the "cheater" into which they plugged UNconnected ATX
supplies;
it had three pairs of connections:
1) A jumper from Ground to PS-ON
2) an LED and resistor from PowerOK to Ground
3) two wires from +5V and ground going into something about the
size
of a small box of matches which was shrink-wrapped to the cable

They wouldn't let me disassemble it !-)
Was there probably a 5-ohm resistor in that box?

Hi Myron, how's the new QTH going?

Plug in an old HD. It should provide enough of a load to get the PS
started and regulating.

Russ - kf4wxd

This link is a good one for using PC power supplies. It
works great. I did it.

Charles, ka8jvx

http://antennex.com/preview/archive3/powers.htm