Page 3 - How to Choose A Power supply

well also some companies like hp use weird psu's in some of their pcs so that without modding your case you can't upgrade all that much

Then they aren't ATX. They are not standardized PSU's, so they aren't ATX, so in that case they won't work with and ATX case unless you modify them. And anyway companies like HP do use standardized stuff. Dell was the one who used to not use them, but they have switched over for the most part.

What about taking your rig to a local PC/computer store, bring also a multimeter with you. Tell them that you are looking for a PSU. You're gonna choose like 4-5, then test all of them, yeah I know they won't like the fact, that you want to test, and so on, but if you've got relationships there, then it's the best. But no problems if they won't let you do, at least you can check if it will fit or no your case. Also you if doesn't fits you can anytime mod your case...

how do i no what kidna psu/psu size i have again?

EDIT* my case is an acerPower S285

Open the side panels of your case and on the PSU there should be a label that is upside down. There should be a figure such as 300w and that is the wattage rating of the PSU. Be sure to check all the amp ratings as well on the 12v line (aka rail) 5v and 3.3v - it might be a good idea to post those here.

ook whats 12v, 5v, and 3.3v mean?

voltages, 12volts 5volts and 3.3volts. not all parts in a computer take the same voltage.

how do u no witch is witch?/
(pictures help alot)

You look at the sticker on the PSU, like i was saying. There should be a grid of some sort on it.

As Jazzy mentioned, there is usually a sticker on the side. However, most manufacturer's adhere to a color standard as well.

i've just find out that my PSU is in the "crappy ones" list, a Codegen 300W... I have used it since 6 years already and never had a problem...

are u having problems?

Thanks for the update martin.

The codegen is a very basic psu that was designed to run a specific set of components. If you tried to stick a half decent gpu and an extra hdd the pc probably wouldnt even boot. And if it did, it would fall over as quick as a drunk man on roller skates.

Absolutely. It's all about the distribution of power on the rails and what it's actually powering. Older PSUs have many more amps on the +5v rail because that used to feed the CPU... now it's 12v and you need a PSU that can supply the required power on that rail.

I've got a 400W Qtec (those godawful gold things) that has been powering a 1300MHz Morgan Duron, a single 7200RPM HDD, 256MB of RAM and a Radeon 9200SE, and all its rails are absolutely spot on. But that's because the machine draws at max about 150W of electricity, maybe less.

Also, I have no idea what the ripple is like... it may be very bad, but it may also be good. The point of buying a good PSU is that when you spend a hole lotta money on newer components, which are much more power hungry, you don't go and buy something that is incapable of powering it all. At worst it may die an undignified death and take some of your brand new equipment with it. Of course, usually, the PSU just dies and that's that, but there's always the chance.

Add iCute to the crummy list.