Desktop PCs: How To Change The Power Supply On a Dead PC

The Dead Body

I came into work a couple of days ago and went to switch my main PC on. Nothing. No life at all. Unfortunately, between the night before and this morning, my PC had died(!) It was an emotional moment for me because it had been a reliable companion since 2006! A true work-horse, modified and improved as and when required during my ownership. I quickly did a mental ‘trial and eliminate’ sypnosis and concluded all may not be lost…

You see, the symptoms were err… absolutely nothing. When I pressed the power button, there were no lights or whirring noises or any kind of output on the monitor. It just stared back at me in complete silence. The light on the monitor was still amber coloured, which told me there was no power going to it from the PC.

It seemed totally dead to the world. I booted up the ‘reserve-‘chute’ (my laptop, actually) and set about doing some primary research online on the subject. It didn’t take long for a ‘plan of action’ to firmly register itself in my wayward head.

The Diagnosis

Usually, PCs have a power switch on the back of the actual power supply itself. Mine didn’t but your best-bet is to check this isn’t accidentally switched off before switching your PC on! It could be something as simple as this, give yourself a ‘kick in the shin’ if it applies to you.

The first thing I tested was the power cable. I replaced it and tried the switch-on, but nothing happened. This was the ‘best-case’ scenario because a power-cable is easy to replace. I double-checked all the various USB/peripherals connections and even tried the PC with only the power cable attached – again, nothing.

Next, I used a multimeter to see if there was any voltage coming out of the 3-pin power connection on the back of the PC. Nothing registered. I was onto something, now…

I rang one of the homies who’s an ‘expert’ in I.T., and he advised me that the most likely component to have failed was the power supply itself. If other things such as the motherboard, RAM or CPU had failed, the computer would have shown at least SOME signs of life, ie: lights flashing, errors shown on the monitor etc.

I learned that the first thing to fail on older PCs is the power supply and the symptoms matched to a T. The multi-meter test registered no voltage, which meant the power supply was dead. Bingo!

The Doctor

I opened the PC’s cover and peered inside. The power supply is usually towards the top of the unit if it’s a tower, or towards the back if it’s a ‘proper’ desktop. I noted down the manufacturer and model numbers of the power supply and other details such as wattage etc. Armed with this, I went to my trusty ‘PC-man’ in my local town-centre. (I totally rejected the idea of buying it online because of the delivery delays due to Christmas). I needed my PC back ‘firing-on-all-cylinders’ NOW!

Inside PC

The engine-bay..

The good news was that there are now available generic power supplies that would replace my original perfectly. Mine was a 300W unit and my-man opted to sell me a 400W one, telling me it’d be better performance-wise. A quick performance-boost whilst we’re at it was certainly welcome!

The new unit cost me £24 which I thought was a great price, since this was me losing my ‘power-supply-virginity’. I had never in my life had to do this before, so I was kinda excited but anticipated a straight-forward replacement job.(!)

The ‘Triple Heart-Bypass’ Surgery

Back in the office, with everything disconnected from the PC and myself ‘earthed’ to prevent electric shock (touch the PC metal cover, work barefoot or wear a special, I dunno, however you do it), I set upon the ‘operation’.

The first thing I did was to note down all the various wires and connections coming from the power supply to the different areas in the computer. If you forget ‘what goes where’, you’ll be ‘up shit’s creek without a paddle’. There’s a main 24-pin connector which you can’t really miss(!) Then there were about six other smaller 4-pin connections including the optical drives, hard drive and so-on.

The old power supply

The old power supply (RIP)

It was just a case of disconnecting the old power supply, unscrewing it from the case and putting the new one in. It can get fiddly with the wire-loom but if you take your time and make sure you do it properly, it’s about half-an-hour’s work – max. There’s no software or BIOS settings to adjust.

I made sure all the connections were properly seated, and routed the wire-loom neatly around the other components. If you’ve got fingers like sausages, and you’re the type who has difficulty pressing a single button on a mobile phone, get your homie to do it(!) I also took this chance to give the whole inside a good dusting.

The Re-Birth

The moment of truth came and I connected everything back up and pressed the power button. Everything lit up like Las Vegas (well, it did to me…) and the machine whirred and buzzed back into life and booted first time. The fan in the new power supply gave off a deeper humming ‘tone’ which sounded fresher than the tone I was accustomed to. Kinda like comparing the different sounds of a V6 and V8 engine on a car. Bravo! The problem was sorted within TWO days and I gained some new learnings. Can’t complain.

Hopefully, as you’ll see, some things in life are more simple than they seem. So, the next time your computer ‘dies’, it just might not be dead.


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