Confused! What kind of PSU do I need?

  symph 22:36 02 Nov 2011

Hi guys,

My PC has stopped working and I'm pretty sure the PSU is the problem, as it's been making weird noises for a while. I'd like to have a go at fixing it myself. It currently has a basic 500W PSU but that doesn't seem to have been very reliable. My PC specs are intel quad core CPU, 8GB RAM, 1GB Nvidia graphics card, 500GB HD, running Windows 7 home premium (sorry I don't have more detailed specs, but I can't boot it to check them at the moment!). I'm not a gamer, but I am a professional graphic artist so my usage is somewhat demanding.

Looking at PSUs online there seems to be a huge variation in price. I see a basic 500W PSU for £8.99 which seems really cheap and I'm not risking that. But then some of them are up to £200! Given the spec of my PC, could someone with more knowledge recommend a PSU to me? Wattage and recomended brand if that makes a difference? I don't mind spending a bit more on something which will improve performance and reliability, but I also don't want to buy something expensive if I don't need to.



  spuds 23:18 02 Nov 2011

"its been making weird noises for a while"

That's probably due to the fan or fans not working properly, and the failure of the psu!.

The replacement would need the same fixing holes, so check the measurements before ordering a new unit.

As for the make and model recommendations, someone else might have a few suggestions and link.

  LastChip 23:24 02 Nov 2011

I have to admit to being a little disillusioned with power supplies.

There was a time when I would insist on something like an Antec which would be pretty much mid range. But in truth, they had a shorter life span than the cheap power supplies fitted by bulk manufacturers.

There is an argument, that more expensive supplies have tighter output tolerances and one should be prepared to pay more for quality.

My findings however, dismiss that as a myth.

I now shove in the cheapest power supplies I can find and don't have any more returns than when I fitted the more expensive ones.

After all, you can fit an awful lot of power supplies at a tenner a piece, when compared to a £200 one.

I wouldn't worry too much. Personally, i always have a "cheapy" spare to hand, so if the current one fails, I can just pop a new one in.

That philosophy may not suit you (and I have no problem with that), but it's simply what I've found over the years.

  symph 10:28 03 Nov 2011

Thanks guys.

I didn't think about the measurements so thank you for mentioning that, spuds.

LastChip, that philosophy sounds fine to me! I may just try a cheap one in that case, and if it works, perhaps get another as backup. After all I'm not 100% certain that the issue is the PSU so it would save me wasting the money (the PC sounds like it is starting up normally, but there is no display or power to the peripherals - no lights come on on the mouse/keyboard/tablet as they usually do when it boots. The lack of power to anything connected gives me the impression that the problem is either the PSU or motherboard, but since the PSU fans have been making odd noises I hope that is the more likely).

Is there any benefit to getting one with higher wattage?



  spuds 11:55 03 Nov 2011

If you check on many of the 'average' computers on sale, you may well find a 350w psu installed. Personally I use 500w 'cheapos' because they are only very slightly dearer than a 350w, depending on the supply source.

With the replacement, make sure that the connectors and cables are the same. They usually are, but its best to check before placing that order.

Perhaps worth a mention, you can get simple plug-in psu testers via eBay and Hong Kong for less than a fiver (7/20 days delivery?). I have two of these and they work very well with a quick test result, as to whether its the psu or other fault causing a problem.

If you buy new from eBay (I do), then be aware that some of the sellers might not have much technical knowledge on the products they sell. Ebuyer or Amazon might be able to offer this technical service?.

  Furkin 11:56 03 Nov 2011

Hi Symph,

I'm no expert at this, but my initial thoughts are:

1/ Size-wise - to me I don't think that 500watt is underpowered, but others may say that it is.

2/ make sure that the PSU is actually faulty. It dosn't matter how cheap they are - if it ain't broke, it don't need cash throwing at it. There are a number of FREE 'monitor' program available to check voltages, temperature, fan speeds etc. I currently use PC-Probe, but there is Everest and of course Sandra will help.

3/ there are lots of things that could cause your symptoms.

good luck

  Fruit Bat /\0/\ 16:45 03 Nov 2011

If renewing a PSU check:

  1. The physical size of your PSU, some are hard to replace due to being a non standard size.

  2. The amount of power need from the PSU don't skimp.

3 The correct connections for your equipment

1. Physical Dimensions

Besides the specs and form factors, the physical dimensions are also important factors in selecting a compatible power supply. Here is an outline of the physical dimensions of most standard power supplies:

ATX: 6x3.5x5.5", HxWxD. Most common. Uses 4 mounting screws.

Mini-ATX: 5x3.5x5", HxWxD. Rare size. Uses 4 mounting screws. Can be used in a regular ATX case, but often not the other way around.

MicroATX: 5x3x4", HxWxD. Use 3 mounting screws. Not interchangeable with ATX or miniATX.

Flex ATX: Even smaller than Micro ATX. Various sizes according to case specs; often not interchangeable.

Use the data above to determine if a particular power supply would fit your case.

The quality of a power supply can be estimated by its weight. While this is not a true scientific or thorough measurement of the power supply reliability, it is nevertheless a very simple and easy way for ordinary PC users to estimate and compare the quality of a power supply. Why weight matters

2. Power supply calculator

3. Correct connections Some boards have 20 pin connectors others 24 pin There is often a 4 pin plug required to power Intel CPUs Molex D plugs for IDE HDD and CD/DVD drives SATA power connections for latest HDDs and DVD drives.

Guide to changing PSU

  symph 12:25 04 Nov 2011

Thanks everyone. I think I've spotted what the problem is - I was checking the internal connections and discovered a pin is missing from the connection of the 24-pin cable running from the PSU to the motherboard (a 23-pin plug, I imagine, is not suitable!). Replacement PSU it is. I think I will get a 550W one, just to be on the safe side. A cheap one is about £15 which is fine by me if it makes my PC work!

Thank you for the additional advice Fruit Bat, mine is a standard ATX and I will be sure to check the connections on the one I buy. I'm sure that tutorial will come in handy when I replace it.

Again, thanks to everyone who responded!


  spuds 13:03 04 Nov 2011

Might be worth checking that the replacement as a 'overload protection' device built in (most normally have nowadays), so if a fault appears, the psu will shut down and not perhaps render the psu unusable.

Also you may find that some ATX psu are advertised as 'silent'. They are until the fan or fans play up!.

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