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 CPU Power Supply to Bench top Supply
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olddawgsrule
Advanced Member


USA
1434 Posts

Posted - February 06 2012 :  15:47:26  Show Profile  Visit olddawgsrule's Homepage Send olddawgsrule a Private Message  Reply with Quote
Here's my conversion of a CPU power supply to a constant bench-top supply.









Old in age, not in mind, so
'Teach me something new'!

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JKSTools
New Member



USA
10 Posts

Posted - February 06 2012 :  18:52:55  Show Profile  Visit JKSTools's Homepage Send JKSTools a Private Message  Reply with Quote
Thats good information. I have a CPU power supply laying on my work bench. I haven't gotten around to tearing it apart yet.
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JKSTools
New Member



USA
10 Posts

Posted - February 12 2012 :  10:03:35  Show Profile  Visit JKSTools's Homepage Send JKSTools a Private Message  Reply with Quote
Hi ODR,

I wired up my CPU power supply as shown in the diagram. The voltage does increase on a volt meter when hooking the +12 to - 12 and the +12 to the -5, but as soon as I connect a slight load the power supply shuts off. I can use it fine for 12v 5v or 3.3v.

JKS
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olddawgsrule
Advanced Member



USA
1434 Posts

Posted - February 12 2012 :  10:29:07  Show Profile  Visit olddawgsrule's Homepage Send olddawgsrule a Private Message  Reply with Quote
quote:
Originally posted by JKSTools

Hi ODR,

I wired up my CPU power supply as shown in the diagram. The voltage does increase on a volt meter when hooking the +12 to - 12 and the +12 to the -5, but as soon as I connect a slight load the power supply shuts off. I can use it fine for 12v 5v or 3.3v.

JKS



2 Things to confirm;

First; Since you're reading the higher voltage on the 'meter' then I have to assume the connection is correct.
Positive says on 12+ and only the negative moves to the 17v terminal.

Second; There was some conversation, on another thread, about 'newer' power supplies having a protection built-in not allowing the 'additional' voltage to occur.

If all is correct with the first, then I have to believe it's the second and I will defer to better minds to get 'us' past this.

Again, if it's newer and this is the problem, then I would like the solution added here.

Old in age, not in mind, so
'Teach me something new'!

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JKSTools
New Member



USA
10 Posts

Posted - February 12 2012 :  12:10:24  Show Profile  Visit JKSTools's Homepage Send JKSTools a Private Message  Reply with Quote
I had the positive connected to the 12+ and had the negative connected to a 12+ and a -5 hooked together. I was also assuming it was some internal protection shutting it off, but the power supply isn't very new. I am guessing it is probably at least 10 or 12 years old.
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olddawgsrule
Advanced Member



USA
1434 Posts

Posted - February 12 2012 :  13:19:29  Show Profile  Visit olddawgsrule's Homepage Send olddawgsrule a Private Message  Reply with Quote
I'm running at least that age, probably a couple more.

I average 4-5years before I replace and that one was 3 back...
Putting it 12-15yrs... 'bout the same..

Hang in there, one of the 'big guys' should chime in on this.




Old in age, not in mind, so
'Teach me something new'!

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Ice_Viper220
Junior Member



USA
176 Posts

Posted - February 14 2012 :  00:48:48  Show Profile Send Ice_Viper220 a Private Message  Reply with Quote
Hey guys,
I have a few old power supplys laying around collecting dust as well I have a few questions, do you get a stable outputs with this? and when you change the voltages from 12 to 24v do you have a decrease in amprage? If so how much. I was considering buying a benchtop power supply but i think i like this idea far better as I do have about 3 or 4 power supplys ranging from 200w to 500w and one of them has a nice 12v rail that will run at 14 amps.

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msmjr
Average Member



USA
444 Posts

Posted - February 14 2012 :  05:23:30  Show Profile Send msmjr a Private Message  Reply with Quote
Hey Guys
I had the same thing happen, with a volt meter I can read 17v and 24v but as soon as you hook it to something the supply shuts off. Kudzu said it could be a safty feature and I think hes right because if you do anything it dosent like it shuts off, so it sees it as a dead short. Ive not resolved this so I hope someone can help.

Growing old is mandatory, Growing up......optional.
He is wise who gains wisdom from another's mishaps.
—Plutius Syrus
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49er
Administrator



USA
4442 Posts

Posted - February 14 2012 :  10:03:50  Show Profile Send 49er a Private Message  Reply with Quote
Hi Ice

You had one question about 1/2 the amps when you double the voltage and YES it is true.

Doug
The sky is not the limit...There are footprints on the MOON.
Your only as DUMB as where your standing.
No matter where you go there you are.
You must be logged in to see this link.
SKYPE bxx49er
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olddawgsrule
Advanced Member



USA
1434 Posts

Posted - February 14 2012 :  15:45:40  Show Profile  Visit olddawgsrule's Homepage Send olddawgsrule a Private Message  Reply with Quote
@Ice; I agree with Doug.
To me it's a wattage thing. Wattage remains. Increase voltage, amperage reduces.
I went to higher voltage to test a theory, of which I'm not settled on.

To all;
We haven't touched the 'sense' wire in this build. I will have to figure out what this does. Some have connected this (how?) and this may be what solves the 'shut-down' problem.
Again, this is only supposition at this point.



Old in age, not in mind, so
'Teach me something new'!

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Ice_Viper220
Junior Member



USA
176 Posts

Posted - February 14 2012 :  23:53:40  Show Profile Send Ice_Viper220 a Private Message  Reply with Quote
Okay that dose it then i am going to build me one of these tonight or well should i say convert me one of these lol. I will post a pic when i get it running or questions if I have problems.

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olddawgsrule
Advanced Member



USA
1434 Posts

Posted - February 15 2012 :  07:53:49  Show Profile  Visit olddawgsrule's Homepage Send olddawgsrule a Private Message  Reply with Quote
Here's a couple of things I read;
These are not 'my comments', just what I've read.

Sounds like some units need a load to run (mine does not).

1) Connect the 5vS wire to one of the 5v wires, and then connect one of the 10 ohm 10 watt resistors between 5v and ground.

Connect the 3.3vS wire to one of the 3.3v wires, and then connect another 10 ohm 10 watt resistors between 3.3v and ground

2) You probably need to have a 10 ohm 10W power "sandbar" resistor between the regular red wire 5v line and ground. You might also need to do the same on the 12v wire or the 3.3v wire. Separate resistors for all lines you want to add a constant load. Different PSU's have different loading needs, you'll have to experiment a little bit. I've even had some people report not needing any load at all!

Some power supplies have "sense" wires which need to be connected to their corresponding voltage wires, but these are uncommon, so connect the 3.3v sense wire to the 3.3v supply line.




Old in age, not in mind, so
'Teach me something new'!

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kcarring
Moderator



Canada
1057 Posts

Posted - May 04 2012 :  23:19:45  Show Profile Send kcarring a Private Message  Reply with Quote


~~~~~~~~~~~~~
You wouldn't laugh at my igloo if you knew how cold my beer is!
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