So you've got a expressionless power supply and want to know why. The problem could be something unproblematic, like a blown fuse or loose wire. If so, you lot might be able to set the supply for less than $i. This commodity will outline how to supercede a bad power supply fuse, saving you the cost of a whole new supply.

WARNING!

Working on a power supply should not be taken lightly or attempted by someone with niggling electric experience. Even when the supply is unplugged, its components can remain charged and Daze You. If you are in incertitude about your abilities, let an experienced repair technician do the piece of work or just replace the unabridged power supply.

If yous do decide to open a power supply, think to UNPLUG IT FIRST. Also, DO NOT WEAR A SHORTING BRACELET when working within a power supply. You do not want to exist in the current path of a discharging capacitor. Remember that power supplies are not the high-dollar items they once were and an hour of a tech's labor is sometimes more the cost of a new supply. If you do feel confident to work on a ability supply, you do so AT YOUR Own Adventure.
Finding the fuse
Nigh power supplies contain very few user-serviceable parts. The ane possible exception is the fuse. Every supply I've opened has independent a fuse. Some are mounted in spring clip holders on the excursion board within the supply equally shown in Figure A. A few even have a holder with a twist-off cap mounted through the supply's housing and are easily changed without removing the comprehend.
Effigy A

Most of them, however, are soldered straight to the excursion board as shown in Effigy B and are not something a novice tech should attempt to supercede. The replacement procedure requires you to remove the circuit board from the housing, unsolder the diddled fuse from the circuit lath, and then solder the new fuse back in place.

Figure B

Working on the underside of these circuit boards in shut proximity to a possibly charged capacitor, shown in Figure C, should not exist taken lightly.

Effigy C

If in doubt about your ability, let an experienced repair tech practise information technology or just supplant the ability supply. Notwithstanding, if you experience that you are competent to practice the replacement, here's how.

Remove and open the supply
To begin, unplug the line-voltage power cord, open up the computer's example, and unplug all the low-voltage cables from all the drives and the motherboard.

Remove whatever peripheral cards that might be obstructing the power supply. Remove the screws holding the ability supply to the case. (Ordinarily, in that location are four of them.) Support the supply every bit you take out the last mounting screw, as y'all don't want to driblet it on the motherboard, and then remove the power supply from the example. Bank check the appointment stamped on the warranty/safety seal (run across Effigy D).

If it is still under warranty, you lot might want to consider returning it for a new unit. If the warranty has expired, you may intermission the seal and open up the power supply. This entails removing 4 to six screws. When separating the ability supply's case, be conscientious not to pare or scrape the wires.

Figure D

Determining if the fuse is bad
Once the supply's case is opened, you volition exist able to run across the major components (run across Figure E). Fuses are commonly found along one edge of the board and are readily identifiable.

Figure Due east

Use an ohmmeter to verify that the fuse is indeed diddled before removing the lath from the instance (run across Figure F). A blown fuse volition take infinite resistance on the meter, while a skillful fuse will read 0.1 to 10 ohms. In one case you determine that the fuse was blown, take a minute to wait over the other components on the board.

Figure F

Any obvious signs of smoke or a burn down marking on or virtually any other component means there are other problems that contributed to the fuse blowing. If that's the case, replacing the fuse volition probably Non solve the problem. At that point, you should forget virtually replacing the fuse and, instead, install that spare ability supply you've been saving.

Replacing the fuse
Having determined that a blown fuse is the merely obvious problem, your adjacent move will depend on how the fuse is attached. If a leap clip holder holds the fuse in place, y'all can hands supervene upon the fuse by using a plastic fuse-puller. If the fuse is soldered in place, your adjacent footstep is to remove the circuit lath from the supply'due south case to access the board's underside.

WARNING!

Handle the ability supply's circuit board by its edges and DO Non affect any of the soldered pins on the bottom of the lath. Hitting the wrong pivot by mistake tin create a shock take chances.
Plug in your soldering fe and set information technology out of the manner while it heats. Double-check the location of the fuse before touching the hot soldering atomic number 26 to its pins to remove them. Some manufacturers print the value of the fuse right adjacent to the fuse on the excursion board (see Figure G), simply some don't. If the value isn't printed, you will take to remove the old fuse to read its values to know which size to reinstall.
Figure Thou

Carefully employ the tip of the hot (most 700 degrees) soldering iron to the short slice of tinned wire soldered to each cease of the fuse and gently button it upward through the printed circuit board as the solder softens (encounter Effigy H). One time the old fuse is free, you tin identify it.

Figure H

To directly attach the new fuse, you lot volition take to solder similar pins to the ends of the new fuse. To practise this, vitrify each end of the new fuse with emery paper to dull the chrome plating. Dab the cease of a piece of stripped 24-gauge wire near 6 inches long with flux and tin information technology with resin core solder. Do the aforementioned to each finish of the new fuse and so solder the wire to the fuse ends.

After making each joint, cut off the tinned wire, leaving nearly œ inch attached to the fuse. Cut off whatsoever excess under the board afterward you accept soldered the fuse to it. Apply the ohmmeter to test the new fuse in one case it is in place.

Instead of resoldering the fuse directly to the board, another option is to install a fuse holder. I started installing $ii fuse holders (meet Figure I) because a two-inch wire is easier for me to work with than one just Πinch long, plus this gets the fuse up off the board and makes replacing it much easier.

Effigy I

If the fuse tests good, you tin put the power supply back together and reinstall information technology in the PC to test information technology. Disallowment other problems, this should bring that dead ability supply to life. Total time for this process is 30 to 45 minutes (plus the time it takes to get a new fuse); total cost for the repair is around 50 cents for the fuse and $ii for a fuse holder, if you lot use one.

Play it safety
Remember, working on a power supply is non for the novice tech. If you're non totally confident in your ability to safely do the job, permit someone else practice it!

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