Computer power supply uses (NOT home repair topic)

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In the days of old, I used to use a mobile CB, which sat on a (designed for it) power supply. The CB was 12 volts DC, and the power supply rectified the house power, to provide DC for the two way radio. And the antenna was on the roof.
An old computer power supply with 12 volt output. Wonder if that would drive a CB mobile, or a CB walkie? Makes me wonder if I could wire a lighter socket to an old computer power supply and have a couple amps of 12 volt DC?
Anyone know how much 12 volt DC a power supply provides? On a survival note, maybe a 12 volt tap off computer power supply could charge up a car battery, or be emergency communications.
I'm Christopher Young
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Won't work
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All the computer PS that I have dealt with won't even fire up unless they are connected to a MB.
That is partly what makes it so hard to figure out if it is the MB or the PS that is dead on a non-starting system.
Colbyt
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Colbyt wrote:

Depends on the supply, they vary a great deal. Use google to locate the specs on a supply. I doubt if most could supply 2 amps of 12V. You might consider a very small battery charger and a small battery (like a motorcycle batt). Look at the label on back of the cb to see how much current is needed. watts / 12 = amps required. If no label, check what amperage fuse the cb has.

That's because the supplies need a load on the 5 volt output. Hang a power resistor between 5V and gnd. some may also require a mometary short between two leads to start the supply.
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Leroy wrote:

Why reinvent the wheel? Rat shack used to sell a perfectly usable $20 bench supply that worked fine with CBs. Just checked, not anymore. Did a quick Google, and found several, that look like like modern versions of what RS used to sell- here is a likely loking example:
http://www.mpja.com/prodinfo.asp?number 02+PS
All depends what your time is worth, I guess.
-- aem sends...
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PC supplies regulate off the +5V,so that needs to have a decent load on it,too. ATX supplies also have a line to the MB for turning the PS on and off.
--
Jim Yanik
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You had just received several replies that don't know what they are talking about.
The older computer supplies that were for the AT type computers work just fine for some 12 volt uses. Usually you need to put a small load on the 5 volt output. I sometimes just use an old hard drive. YOu have to look on the supply to see how much current you can draw out of the 12 volt side. All wires of the same voltage and poliarity hook together inside the supply.
For the ATX supply: Hook up a load to the 5 volt line. Old hard drive again.
Jumper pin 14 (PS-ON) to pin 13 (ground, black wire.) At this point, fan in PS should start spinning, drives should spin, and + 5/12v, -5/12v, +3.3v, and +5vsb should be present at 20 pin connector.
Disconnecting pin 14-13 jumper should turn supply back off.
The supplies will put out from 5 to about 10 amps or more depending on the supply on the 12 volt wires, 20 or 30 amps on the 5 volt wires and not much on the minus voltage wires, look at the side and see if they list the current.
YOu may be able to open up the case and turn up the voltage some. Many mobile radios usually operate best around 13.8 volts as this is the nominal voltage of a running car. Also as they are switching supplies the may put out a signal on the frequency you are trying to receive. Short answer is you probably can run the CB on the supply, and yes if you do turn up the voltage. I use one to test some 2 meter ham radios when I don't want to hook them up to my regular DC supply. I did turn the voltage up some with the internal adjustment. Don't recall, but think that voltage pot is for all the voltages.
YOu probably can not charge a 12 volt battery as you must have some more voltage than 12.6 volts to charge the battery.
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Ralph Mowery wrote:

It's worth a try, I run a "Jigged up" AT supply that gives me 14v at greater than 10amps to charge batteries.
Rheilly P
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At present, that's more complicated than I want to go. Thanks for the details information. But, I'll find a different power source.
--
Christopher A. Young
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Stormin Mormon wrote:

GEEZ! I wish more people understood electronics. Computer power supplies are very useful for many do it yourself projects and the fact that they are mass produced makes them very inexpensive for the experimenter. I wish they were around when I was a kid drooling over the the thought of having a high output regulated power supply for my Frankenstein like projects which I would recruit one of my little brothers to plug in while I ducked behind something. Here is a link to a site showing how to convert a computer power supply for bench top use:
http://letsmakerobots.com/node/1355
[8~{} Uncle Monster
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Exactly. Last year a young licensed amateur friend and I dug through our old computer switching power supplies and then modified one for 12 volts around 15 - 20 amps (about 200+ watts).
Yes we had, in that case, to put a resistive load on the +5 volt output, comprising two 4 ohms ceramic resistors (because had plentiful supply of them) in parallel mounted on the metal case acting as the heat sink. i.e. 5/2 = 2.5 amps worked nicely.
At last report it was powering his ham rig without extraneous noise on amateur band frequencies; had thought at one point we might have to add another 'hash' filter to the 12 volt output, but not necessary.
Some of those discarded switching power supplies (probably operating internally up to 20 kilohertz) are quite powerful; up to 400 watts for example! And compared to 60 or 50 hertz 'analog' more compact and lighter. We have put another switching power supply, requiring fewer modifications on our boat as a battery charger. Adding a fuse in the 12 volt output lead. Input is 115v at 60 hertz when plugged into a dock.
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That assures me that I won't just cut open the case, and find 12 volts some where. Well, that job is gone for naught.
--
Christopher A. Young
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Stormin Mormon wrote:

Hell, you don't even have to cut open the case--the leads are there w/ connectors to probe which are which (if you don't already know).
All that is required for a switching supply is to have the minimum load for stability.
The only thing done in that case was to clip of the 'puter connectors and connect the wahrs to panel mount jacks.
--


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On 9/11/2008 4:40:13 PM, "Stormin Mormon" wrote:

I don't see why you've become discouraged. It's really very simple to rig. You don't have to do the elaborated mods in that link -- you don't even have to open the case. Any one of the standard molex connectors has the voltages you need
http://upload.wikimedia.org/wikipedia/commons/thumb/3/31/Molex_female_connector.jpg/800px-Molex_female_connector.jpg
The yellow wire is 12v and either of the blacks are neutral/return/ground.
Here's a discussion of the molex connector http://en.wikipedia.org/wiki/Molex
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On 9/10/2008 11:52:13 AM, "Stormin Mormon" wrote:

I don't see why not. Twelve volts it twelve volts. I wouldn't think a CB radio would require any super regulation and computer power supplies are pretty clean.

They usually have a label on them giving their output. Here's an example
http://static.howstuffworks.com/gif/power-supply3.jpg
But, even a super cheap one should be plenty to run a CB radio.
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On Fri, 10 Oct 2008 15:38:21 -0500, "jim evans"

Just remember, you need a resistive load on the 12 volt line before you get ANY output on most supplies.
The 250 watt AT supply I have sitting on the bench puts out 11 amps on the +12 side.
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clare at snyder dot ontario dot canada wrote in wrote:

that would be the FIVE VOLT line.That's what most PC supplies regulate on.
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You are correct. Minimum 500ma load on the +5 required for stable voltage output on +12. I always just threw an old hard drive on when checking out a power supply (or trying to test a motherboard - MB alone in about 99% of cases was not enough load to start, and if it was, it was not enough load to regulate properly and half the time you didn;t get the required "power good" signal.
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On Fri, 10 Oct 2008 23:19:52 -0400, clare at snyder dot ontario dot canada wrote:

Why not just a 10 ohm wire wound resistor.
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On Sat, 11 Oct 2008 00:38:27 -0400, snipped-for-privacy@aol.com wrote:

Because I always had a hard drive around and it had the right plug on it.
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