Power Supply Question 1

[WestCoastKid]

I have a power supply in my dell dimension 4400, that sounds like the fan is about to go.
I have an old Optiplex Gxa (tower) that I don't use any longer. Based on the following links is it safe to say that I can use the power supply from the Gxa to replace the PS from my Dimension?
I'm not a complete knucklehead however I don't want to goof on something like feeding electricity into my workstation.
Thank you.

http://support.dell.com/support/edocs/systems/dim4400/techov.htm?c=us&l=en&cs=&s=gen#1101836

http://support.dell.com/support/edocs/systems/dfuj/power.htm?c=us&l=en&cs=&s=gen

 

[rclarke250]

quick answer is no it won't work, the older power supply lacks the ATX 12v 4 pin connector. that is required for the P4 system board. Are there ways to rig it to work? Yes. should you try? No. try ebay, or search with google to find a compatible power supply. Note: It is possible to just replace the fan, but you need to know what you are doing, as there is a shock hazzard inside all power supply's, even after power is removed.

 

[edfair]

Looks like it is short on power. +12 is about half of what the diminsion has. 3.3 is short also. Whether it is all needed is another question.
Why not replace a fan?

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[garebo]

Its pretty easy to replace the fan as edfair suggests. There is a part inside the power supply that has to either be discharged or not touched, or you could get a shock. I dont know which part so i just wear rubber gloves and work carefully. Its fairly easy to replace a fan without getting a shock. I havent ever got a shock but i know you can, same as with a monitor or tv on the inside, even unplugged. If the power supply hasnt been running for a while the charge inside it dissipates but i dont know how long that would take, so its best to just be careful.

One more thing, though. Some Dell power supplies and motherboards were or are wired different from standard ATX specifications. So if you arent going to install a new fan in your power supply and you plan on getting another, you might want to double-check and make sure your current dell unit is using a standard ATX power supply. I have heard that some of the newer dell computers are using standard ATX power supplies, and maybe all of them are, i dont know.


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[tt7601]

also, you can call up dell and they have replacement parts for older systems, call them up and see, power supply fans for replacement from dell aren't expensive and also if you do replace the fan on your power supply, drain the flea power by unplugging the computer from the wall outlet and then pressing the power button for about 5 to 10 seconds.

 

[electronicsfreak]

The charge in the coils can be held for years. lol so best to either discharge or not touch them.

 

[garebo]

Good tip regardless but i dont think that drains all the power from the power supply. Last time i changed a fan i simply wore rubber gloves and used electrical tools (rubber handles). That way, if you are careful, you wont get a shock.
You could likely get a free, used fan from any computer shop.


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[garebo]

electronicsfreak, i was posting in reference to tt7601's post. In this case, i dont think there is any harm done, just to let you know.

At this point its safe to say we all know there is power inside these power supplies even though they are outside the case and not plugged in and that one has to be very careful. I think we have made sure he or she is aware of that, how to work around it, and that one can put another fan to replace a bad one.



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[electronicsfreak]

I realize that garebo sorry if you got the wrong idea lol. Wasnt trying to undermine what you said.

 

[garebo]

Not at all, it was the other way around. I wanted to make sure you didnt think i was undermining you, lol!!
Anyway, we are squared away here. You certainly did no undermining at all anyway!!
But that is what is so great about this forum and i hope it stays that way. The others are full of loud-mouth idiots, whose only vocabulary is 4 letter words, without them they cant speak. And this place is so far above that, its a wonder they let me in!


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[DDA113]

Just to put the record straight, the kind of power supply you are talking about is what’s called a “Switch mode power supply”.
The PSU works by taking MAINS voltage, feeding into a full wave rectifier then to a CAPACITOR.
The first DANGEROUS part of the circuit is this Capacitor, at this stage you have in the region of 600v DC – DC is NOT forgiving, it will cause muscles to lock up, the 600v part BURNS the skin.
However the charge on the capacitor in this size of PSU only lasts for minutes. So to be safe leave it OFF for an hour should cover it. If you have a meter look for the LARGE Capacitor near the mains input, and measure its voltage.
Someone mentioned that the “coil” can hold a charge for years – not so, a coil can’t hold a charge as such. It can give a voltage ‘back out’ but it is only due to a collapsing magnetic field, consequently it is a ‘short lived’ voltage.
Don’t short circuit the capacitor to discharge it, massive currents will flow possibly damaging the capacitor or other components.
The next DANGEROUS part of the circuit is the CHOPPER, this takes the 600vDC and ‘chops’ it up at about 40KHZ, this area can cause RF (Radio Frequency - like a microwave) burns.
This is then passed through a ‘small’ transformer, reduced, rectified and regulated to give the low voltages required by the PC.
The whole system is extremely efficient due to the high chopping rate.
A transformer would have to be very large to pass the same amount of current.
I have worked on many a unit, but I still respect them.
DO NOT POWER THE UNIT ON WITHOUT THE COVERS IN PLACE, UNLESS YOU KNOW EXACTLY WHAT YOU ARE DOING.
However changing the fan should be straight forward, as you don’t normally have to remove the PCB (Board) from the case, so you can’t get to the ‘live side’.

 

[edfair]

One small caution: high voltages can show up on heatsinks also, depending on how the power supply is built.

To keep from working in the board connections you can cut the existing fan wires near the fan and use small wirenuts to join the existing wires to the new fan wires. No need to cut the new ones short, just fold them up and put in the box in such a way they don't get chewed by the fan.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[garebo]

The heatsink part makes sense, as in a short?
Great piece of advice on the fan wire and wirenuts!


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[felixc]

The fan got noisy? Want to try something easy first? Disconnect the power supply from the mains, wait a day, open it, unscrew the fan off from the power supply, carefully remove the sticker from the center. Don't throw the sticker away. Under this sticker is where the bearings are. Just add a drop of oil on the axle, turn it a bit with your fingers. Put back the sticker, put back the fan in place. It can work for another year or two. It worked on mine, and on some others.

 

[garebo]

I do that all the time, but instead of oil i use graphite powder and just add a bit of oil to the graphite to help it get in the fan better. YOu can also buy graphite oil but i prefer using the graphite and adding a bit of oil to it.

The reason graphite works much better is because regular oil dissipates over time due to heat and friction, the graphite does not. But oil does spread the graphite around a bit easier. And being the whole power supply is so important, and replacement fans are so cheap, i figured you might want to simply replace the fan instead of oiling. In addition i have received undo criticism for my beliefs, another reason i didnt post this.

Bottom line on this. I learned about the graphite trick some 6,7 or 8 yrs ago. I have used it on all fans and it works. I had found that fans, when oiled, only lasted another month or two and started acting up again. But when i added graphite to the oil, or simply bought graphite oil and applied that, the repair lasts basically forever, or at least until the fan just wears out and the bearings totally shot, lol. I have done this on power supply fans, case fans, and those small fans that are common to ide removable trays. These fans tend to start making loud noises about a year after purchase. And the graphite really does the job.
I buy the graphite powder in a small tube and the graphite oil is often in a small plastic squeeze bottle.
You can get the stuff at all auto stores and some hardware stores. You can buy them in very small tubes and the cost is about $3 or so.



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[felixc]

Nice tip about the graphite powder! I'll try to remember when I see it in a store.

 

[garebo]

Thanks very much and trust me, its worth it. I forgot to mention that i put it in almost all my fans now, even new ones. First it prolongs their life but it also makes them quieter as well.
Again, though, there is graphite oil and plain graphite powder. As long as you get graphite powder you can use either graphite oil with it or regular sewing machine light oil, either one. For me, the key is the graphite powder as it stays in there forever.

I also forgot to point out use lots of paper towels, cotton buds, etc, as this stuff stains badly on your clothes. Your wives will wanna have my head on a platter!

The graphite powder and graphite oil are the best for locks and hinges as well. Any place you have metal on metal contact.

Thanks again for the star!

Good advice + great people = tek-tips