Well, I somewhat agree with both dudes. However, having 350 watts at your disposal does not assure reliablity by no means. Neither does 250 Watts. Look at the specs on a power supply. Take a look at your 250 Watt supply. It can pump out 20 Amps into its 5 Volt bus if it had to but I guarantee it doesn't because the computer does not demand 20 Amps from this bus. It might draw 10 Amps. Look at its 2.x or 3.x Volt rating. It probably states 10 to 15 Amps. Again, the CPU might draw 2 to 3 Amps at best but usually draws only about 0.5 Amps unless its an AMD, which draws more current than Pentium. Why can power supplies put out so much current? Simple. It's because they can with the electrical components used and it's actually cheaper to put out high capacity power supplies than weaker ones because it's cheaper to design a single power supply with high capacity to drive low and high current loads than to build a custom supply for specific ranges of loads. It also means that the more robust a power supply is, the cooler it generally runs when only a small percentage of its rated capacity is drawn upon. At 250 Watts, the power supply cannot even feel the current being drawn by the entire computer. A computer fully loaded with 128 MBytes RAM, 32 MByte RAM AGP screaming 360 MHz RAMDAC VIDEO, SCSI, NIC, SOUND, MODEM, PCMCIA, FLOPPY, CDROM, CDRW, and 2 harddrives might draw 1.5 Amps from this power supply. That translates roughly to 170-180 Watts. In total, all the drives I mentioned have motors powered by the +12 Volts from this power supply. All induce surge currents that the power supply must cope with. Power supplies can deal with surge currents becasue they are short term. A power supply is rated mainly to its ability to dissipate heat. Once in a while surge currents don't cuase power supplies to heat up. So if all of these motors were to spin up to speed simultaneously, this would be the only real surge strain the power supply must contend with. This usually occurs at boot up time. Look at the max current draw from all your motor driven peripherals and add them up. If their total exceed the power supply, then go find one that can handle this maximum surge load on the +12 Volt bus. You may find that the max surge doesn't really go that high. Generally, the spin up current on these devices exceed one or possibly 1.5 Amps at 12 Volts. This translates to 12 to 18 Watts. Your 250 Watt supply probably states 10-12 Amps for the 12 Volt bus. The +5, +5 standby, -5V and -12 Volt busses are never under a strain in these power supplies. The biggest problem with getting a power supply is making sure you buy a good one, say around $40. Don't go for the biggest, go for the best and maybe one with a ball bearing fan because those fans last a little longer. For sure, any will power supply will power your computer providing it's a good one. So what's a good power supply? Don't ask me. I'm not certain. I've never had to replace one. Maybe I'm lucky. I've got friends who have replaced theirs but they just went and got another one without regard to its quality and never had further problems, so I don't know. I think ACER is a reputable brand. There are others as well. A good power supply is identified by its ability to regulate its output Voltages without being loaded. This capabilty requires better designed switching circuitry and no short cuts on the design. Unfortunately, most ATX power supplies will not even switch on unless they are plugged into a mother board. So you're screwed on determining this yourself with a multimeter. In the old AT days, it was known that if a power supply was switched on without being connected to a mother board, it would self destruct because of the output voltages ramping to a level above the rating of the electronic components in the supply. They had to be connected to a light bulb for testing to prevent this from happening. Have fun.
|
0 
