How to replace a power supply?

[threexgreen 3,135]

Hello,

 

I've decided to buy myself a new GPU the other day. To run it however I need a more powerful power supply first, min 600W. Now I took a look inside and found that there are a bunch of cables going everywhere from the power supply (of course). I suppose you keep those cables plugged into all the components and connect them to the new power supply. I'm not sure though how to disconnect the cables from the old power supply. They go inside the power supply tied together as a whole. Could someone enlighten me please?

[Luke 782]

I suppose you keep those cables plugged into all the components and connect them to the new power supply. I'm not sure though how to disconnect the cables from the old power supply.

 

You have it backwards. The power supply and the cables are typically connected. Disconnect the cables from the components. The new power supply will come with its own cables.

 

Cheers!

 

Luke

[neucoas 82]

maybe this will help you

 

[JRBarrett 3,050]

With your current power supply, the cables are part of the supply, have to be disconnected, and removed with the PSU when it comes out of your case. This kind of power supply has every possible kind of connector on its various cables, and many of them are probably unused.

 

Better quality replacement supplies are "modular". Rather than a rat's nest of permanent cables, a modular supply has a row of sockets on the back side, and will come with a large assortment of cables that plug into the sockets, with the proper ends to connect to your motherboard, GPU, hard drives, case fans etc. With a modular PSU, you only connect the cables you actually need for your particular installation.

 

If you are not experienced in replacing a PSU, it might be best to have the job done by a local computer shop, or perhaps you may know someone with system building experience who can walk you through the process.

 

If you purchase a new PSU online, be sure that it is indicated as "modular" in the tech specs. There are still high-end PSUs being sold that are NOT modular, (like the one you already have).

[carlito777 712]

To be honest: If you don't know how to replace a PSU (which is probably one of the easiest repairs on a PC), you maybe shouldn't mess with these things. This is not meant to be harsh. Just trying to prevent you from srewing up your system big time. Connecting the wrong plugs can lead to catasthropic failure of the system. Seek help from someone who knows how to do these things.

[martin-w 3,234]

On the other hand... we all have to start somewhere. So why not with one of the easier tasks?
 
There are non-modular PSU's with all cables attached - lots of bulky unused cables remain in your enclosure.
 
There are semi-modular PSU's with some cables attached, usually the ones that need to be attached anyway - fewer unused cables to block airflow in you enclosure.
 
There are fully modular PSU's with no cables attached - minimum cables in your enclosure.

 

If you decide to have a bash, watch as many YouTube videos as you can find, read your motherboard manual if you have one [download one form the motherboard manufacturers website if you haven't] ask lots of experts here, read as many tutorial as you can find on the internet.

 

Watch out for electro static discharge, take your time, stop if you are bemused and ask us.
 

[Luke 782]

Connecting the wrong plugs can lead to catasthropic failure of the system. Seek help from someone who knows how to do these things.

 

The plugs are all keyed - you physically cannot stick them into the wrong location without using enough force to break the plugs. Agree with martin-w; this is about as easy a task as you can do.

 

Cheers!

 

Luke

[brynjames 0]

Be very careful to ensure the new power supply has all the connectors available for the components you have to feed.  Different PSUs come with varying numbers of different connectors.

 

Bryn

[threexgreen 3,135]

Thanks all for the replies. The GPU demands min 600W, is it sufficient to buy a 600W device or should I go for more to be sure?

[gfd 15]

It can't hurt to buy a power supply with higher wattage. Less strain on the unit and capacity for growth in the future. Don't know how large your case is, but buy quality and buy watts. Low cost investment pays off.

[Luke 782]

Thanks all for the replies. The GPU demands min 600W, is it sufficient to buy a 600W device or should I go for more to be sure?

 

You can probably get less.

 

The reality is that most no-name power supplies suck, and don't provide enough current on the 12V rails. The video card manufacturers don't want to get into the swamp that is defining "good" versus "lousy" power supplies, so they ridiculously over-spec the power supply requirements.

 

To give you an idea, I have an overclocked 4770K with 32GB of RAM and a GTX 760. Even when FSX is maxed, I can't get it to pull more than 200W from the wall. Given an 80% power supply I'm pulling at best 160W into the system (and probably lower since they hit peak efficiency near max load).

 

Get a good power supply, not a big one. Seasonic is a great brand. If you get a big power supply you're wasting money and wasting power, since they're less efficient at lower load.

 

Cheers!

 

Luke

[martin-w 3,234]

Although I agree in principle with Luke, I would avoid anything less than the recommended wattage. Surplus power is a good thing in my view, less heat so less degradation, lower fan speed and peace of mind of course.

 

I would say trust the PSU calculators.

 

Don't go bonkers though.

 

I'm a fan of Enermax PSU's at the moment.

[Luke 782]

Surplus power is a good thing in my view, less heat so less degradation, lower fan speed and peace of mind of course.

 

You don't have surplus power, you have surplus capacity - and I don't understand why you would have less heat if you had more PSU capacity. Heat is entirely a function of PSU efficiency, not capacity, and PSUs are generally more efficient at higher loads.

 

Let's say we have my system, running with either a 400W PSU and a 750W PSU. In both cases, I'm pulling around 160W from the PSU. If the 400W PSU is running at 80% efficiency and the 750W PSU is running at 75% efficiency, then in the former case I'm turning 40W of power into heat, and in the latter I'm turning 53W of power into heat. If you're really concerned about heat, you should focus on the efficiency of the power supply. Going from 80 to 90% efficiency should save around 20W of heat.

 

Of course, this all pales beside the heat and power savings going from a 5xx to a 7xx series nV card.

 

I would say trust the PSU calculators.

 

Only in the sense that they're about 100-200W more than necessary. Look at the actual specs of the card. Here's the GTX970: https://www.evga.com/Products/Product.aspx?pn=04G-P4-2978-KR

 

You'll see that the max power draw is 170-200W, depending on the model. Combine that with an i-4770K with a max TDP of 84W, and a decent 450W power supply can more than supply it (you're not going to be using more than 30-40W for anything else on the system). Same thing with my 760 - it's max draw is 170W and I've never come close to matching that. nVidia claims that the minimum power supply required for a 760 is 500W. They only do so because most cheap power supplies can't crank out 170W on the 12V rails, so they overspec something ridiculous just to be safe.

 

I agree with you that our disagreement is very, very minor. Unless you're doing SLI or something exotic, a good 450W or more power supply should be more than adequate for the job. Getting one rated at 90% or so should reduce the heat some more as well - reading power supply reviews for efficiency and noise might not be a bad idea either.

 

Cheers!

 

Luke

[vgbaron 3,510]

Be aware that you can have a PSU with the *total* wattage that will still not handle your GPU. This can get confusing. Luke mentions the 12v rails - that is usually where newbie get into trouble. Many gpu's require 12v/20a ( 20a on the 12v rail - if your 600w PSU is set up with 12v/14a - the GPU will not run.

 

Depending on what you plan to run, I'd say nothing less than 16a on the 12v rail but check your video requirements.

 

 

Vic

[martin-w 3,234]

Quote

Be aware that you can have a PSU with the *total* wattage that will still not handle your GPU. This can get confusing. Luke mentions the 12v rails - that is usually where newbie get into trouble. Many gpu's require 12v/20a ( 20a on the 12v rail - if your 600w PSU is set up with 12v/14a - the GPU will not run.

 

Depending on what you plan to run, I'd say nothing less than 16a on the 12v rail but check your video requirements.

 

 

Vic

 

True, but that doesn't usually pose a problem in regard to multi-rail designs as long as we consider what plugs into which rails. Absolutely right that you should mention it though.

 

It may be a multi-rail PSU with less amps than required on a "single" 12v rail, but multi-rail PSU's have more than one 12v rail, with PCIe power cables being fed from two or more rails. Almost all Enermax PSU's for example are multi-rail as opposed to single high amperage rail designs. The Enermax 850 has no less than 4 12v rails. Modern multi-rail PSU's are designed for top end graphics cards and even SLI despite having lower amperage on a single rail.

 

Multi-rail designs tend to be better in terms of overcurrent protection too, because a single rail design has more capability to deliver much more current into your components.. So I think it's more about quality and suitability for your rig than multi-rail or single rail these days. But as I said, we should still consider carefully which components we plug into which rail if we opt for multi-rail.