Whether one is building a computer from scratch or trying to resurrect an old friend, choosing the correct power supply unit is critical. The power supply unit not only provides power for the machine, it also regulates the energy as it comes through the cord and smooths out minute surges the surge protector did not detect. Grabbing the first one on the web search is not recommended.
Instead, consider the reason for the unit. Perhaps one is trying to salvage an old computer. There may be documents or programs still valuable on the hard drive and without a new power supply they will be lost forever. The first suggestion is to go ahead and take the plunge – open the computer case. A can of compressed air could be helpful if the model number is not legible. Write it down and search for it. If that model has served well, it may be best to simply replace it.
If one wishes to upgrade the power supply unit, be sure to look at wattage. Substituting a 300 watt power supply for the old 500 watt unit could prove disastrous for the processor. While one unit may look like any other, try comparing two by weight. Often the lighter weight units have used lighter weight wires or connectors and may have a shorter shelf life than those with heavier components. Also be careful the new unit has the same number and type of connectors as the old one. The mating parts on the computer will be harder to replace, so a little care and research before purchase can save a lot of heartache.
Let us say one wishes to build a home computer from parts. Then the power supply unit has no restriction. Several sites have power supply calculators which allow the user to type in what other hardware is going into the computer and will suggest an appropriate power supply. Unfortunately, these calculators are not always aware of the size of the case and may recommend a power supply too large for the system. Measure carefully in metric units and read the specs on the sale site. Nothing is more frustrating than being ready for assembly and the parts do not fit.
All that is left is to consider one’s budget and need. Consider the reason for the computer. Is it a monster machine with high end processors and programs designed to make cgi look obsolete? Then consider a high end 1000 watt power supply. These can be purchased for $200 to $400 at reputable dealers. On the other hand, this computer has quite a few bells and whistles and makes on-line games look terrific, a 500 to 750 watt unit may suffice. The good news is the mid-range units have dropped in price to under $100 and often can be found for as low as $40. There are lower wattage unit available, but since the difference in price is just a few dollars, the only reason to reduce wattage would be for size constraints.
With current web tools, one can find easy to follow tutorials for power supply unit installations. All it takes is patience, a web browser, a budget and a clear idea of what one wants.