List of power supplies known to kill devices - Page 1
Forum section: electronics / repair

author: FileNotFound__
author_rank: Contributor
timestamp: May 15, 2022, 12:37:37 am
content: Today I got a computer for service, totaly dead.After some investigation, I mesured 8v on a 5V standby rail.Replacing the power supply did nothing.The motherboard killer in my case - Bestec ATX-250-12E -This is defenetly not the first time I saw a bad power supply kill a motherboard so I decided to be smart and hopefully help some people avoid thoose power supplies by making a list that on whitch anyone can share their expiriences with power supplies killing electronics.If you post your expirience here, preferably mention the brand and the model of the supply.Questions about power supplies you are planing to buy are also welcome.

author: Haenk
author_rank: Super Contributor
timestamp: May 15, 2022, 01:25:36 pm
content: Remember, those PSUs are sold in huge quantities, some series certainly into the millions. So it won't be hard to find reports on defective units of any brand or model - making a list pretty pointless.Plus: This PSU is 20 years old, which is longer than what I consider a normal lifespan of a modern computer, though these probably already failed a lot 10 years ago.

author: Simon
author_rank: Unknown
timestamp: May 15, 2022, 01:28:13 pm
content: So the 5V standby rail from the PSU gave 8V and you blame the motherboard? was this to be a list of power supplies or motherboards? There is no point in this thread.

author: Stray Electron
author_rank: Super Contributor
timestamp: May 15, 2022, 01:29:48 pm
content: So you found exactly ONE power supply that killed a motherboard? That hardly makes all of that type PSUs "killers".Sample size of one and all of that.

author: Simon
author_rank: Unknown
timestamp: May 15, 2022, 01:41:55 pm
content: well reading his post it's a PSU killer motherboard but it's the PSU's fault......

author: Skyfox
author_rank: Regular Contributor
timestamp: May 15, 2022, 02:17:17 pm
content: In the retro computer world, Commodore power supplies are notorious for going bad and destroying the computer. Many of their power supplies were potted, filled to the brim with epoxy that held all the heat in. After a few years the 5V regulator would go out and pass 12V through, destroying the chips on the board one by one. Some early Commodore power supplies and some aftermarket supplies were not potted and could be opened up to repair, but the bulk of them were potted.These days there's what's called the "C64 Saver" circuit that will cut the 5V line if it detects the voltage getting above about 5.3V, and it's absolutely essential to use one of those if using an old potted power supply (or any supply for that matter, since even a non-potted supply could go bad and fry chips). I have a couple of the non-potted supplies, and in one of them I installed a little C64 Saver board that's barely more than 1 square inch in size, so that supply will always be safe to use. For the potted supplies I have a saver that can be added in-line with the power cord. Building up the circuit just takes a bit of tweaking to get just the right resistor in the detection circuit because as the zener diode warms up it starts dropping the voltage limit, and it will unexpectedly cut power despite no actual fault.

author: bostonman
author_rank: Super Contributor
timestamp: May 15, 2022, 02:48:36 pm
content: QuoteI thought the potting material used dissipated the heat to the case?

author: FileNotFound__
author_rank: Contributor
timestamp: May 15, 2022, 02:55:36 pm
content: No, it was the overvoltage on the 5v rail that killed the motherboard.I've seen theese things happen before and what I wanted was to create a list of power supplies to avoid, but people will always find junk to complain about even before trying to understand the point of the original post.I mentioned only one power supply because it is the one I have expirience with and seen other people complain on the internet about the same issue.Thank you for reminding me why i hate using forums.

author: Simon
author_rank: Unknown
timestamp: May 15, 2022, 03:12:01 pm
content: eventually any power supply will go bad, so your list is simple: all of them.Years ago a couple I know had their hard drive fail. Very luckily for them I got a new PCB and fixed the drive. I just assumed that this was a common thing. Then months later they called me back with more problems. This time it was the power supply and I think the 12V was doing 18V or something. I concluded that the original problem wit the hard drive was in fact caused by the power supply. I did not make a note of this bad power supply, the computer was so old that you could not complain.

author: wraper
author_rank: Unknown
timestamp: May 15, 2022, 03:17:54 pm
content: Quote from: Simon on May 15, 2022, 03:12:01 pmDecent PSU fails gracefully and does not kill the load it powers.

author: Simon
author_rank: Unknown
timestamp: May 15, 2022, 03:19:59 pm
content: Quote from: wraper on May 15, 2022, 03:17:54 pmSince when did they start doing this? I'm talking something real old. Ultimately if it does not come from a decent brand I'd not trust it. I have a bequiet PSU that is over 10 years old and will power a PC with modern GPU and all, but at the time it cost me 40 quid when I could have paid a tenner.

author: wraper
author_rank: Unknown
timestamp: May 15, 2022, 03:26:45 pm
content: Quote from: Simon on May 15, 2022, 03:19:59 pmEven models from reputable suppliers sometimes have some flaw which cause them to fail in destructive way. For some PSUs increasing the output voltage is the most common failure mode.

author: BBBbbb
author_rank: Unknown
timestamp: May 15, 2022, 03:28:18 pm
content: Quote from: Simon on May 15, 2022, 03:19:59 pm"Decent brand" can be misleading, a lot of rebranding going on in that segment.For those unfamiliar, jonnyguru website used to be an amazing resource for picking your new PSU, but unfortunately Jonny had to pull the plug on it. Not sure if there is a similar resource available now.

author: bostonman
author_rank: Super Contributor
timestamp: May 15, 2022, 03:46:34 pm
content: From my experience, I find most power supplies use bare minimum rated components such as capacitors.They'll go with 85 degrees C and voltage ratings just under double the working voltage. While 85 degrees C is quite hot, the closer to this temperature, the shorter lifespan of the capacitor. When I replace capacitors, I always go with 125 degrees C and higher voltages (providing they physically fit).Also, power supplies are so tightly packed that the design requires a good balance between component location and dissipating heat to the casing.If power supplies were designed better, they'd last longer, but the price will increase. A computer power supply can be designed without a fan, but the heat sinks would be quite large (unless the transistors were mounted to the computer tower case). Unfortunately we live in a throw a way society. Years ago you bought a TV that lasted twenty to thirty years. Now the TV goes bad in five-years, the repair price is 75% of the cost, and you discover the new TVs are more modern thus making it not worth repairing an old unit.

author: FileNotFound__
author_rank: Contributor
timestamp: May 15, 2022, 04:09:58 pm
content: Example of a Bad new power supply, with a ripple high enough to cause instability, and an example of a Good old power supply that I use as a bentch supply.The controll chip is the same, same frequency, same vaweform, but a huge difference in the output ripple, 100mv of AC is almost out of spec for an ATX standard from 17 years ago...

author: TheMG
author_rank: Frequent Contributor
timestamp: May 15, 2022, 04:21:28 pm
content: The only surefire way to completely prevent an overvoltage failure would be to have a crowbar circuit on all outputs of the power supply. Something which is extremely uncommon especially in consumer electronics as it's extra components on the BOM which means additional cost.That being said, on a well designed modern power supply this is an extremely rare occurrence.What we're talking about here is pretty much a dinosaur of an old cheap ATX computer power supply, and I'd guess the +5VSB supply is likely a pretty primitive self-oscillating flyback circuit, those are prone to doing all sorts of bad things when the capacitors dry up.

author: TheMG
author_rank: Frequent Contributor
timestamp: May 15, 2022, 04:27:19 pm
content: Quote from: FileNotFound__ on May 15, 2022, 04:09:58 pmI've never seen a Corsair branded power supply that looks like that nor can I seem to find anything similar on a Google image search. What's the model number? Are you sure it's a genuine Corsair? It could be a cheap counterfeit knock-off which has sub-standard components.Actually looking at the specs for the output currents I can almost guarantee that is a crappy new-old-stock generic ATX power supply that someone has slapped a corsair logo onto. With only 13A available on the 12V rail, it's a very old design. Relatively modern computers (anything in the last 15+ years pretty much) draw most of their power from the 12V rail, and very little from 5V and 3.3V.

author: FileNotFound__
author_rank: Contributor
timestamp: May 15, 2022, 04:32:33 pm
content: It is not a corsair, it is a sticker I made as a joke and forgot to remove.You can probably see the colour difference between the background of the logo and the original sticker.Sadly, most of cheap power supplies are built that way, not because of old stock, but because it is cheap to do so, that way they can put big numbers on it and pass the quality inspection.

author: FileNotFound__
author_rank: Contributor
timestamp: May 15, 2022, 04:41:37 pm
content: The main controller IC on a power supply, for example the most common one tl494 or its equivalent ke7500 have the ability to monitor the output voltages, but most cheap power supplies found a cheaper alternative.

author: MK14
author_rank: Super Contributor
timestamp: May 15, 2022, 04:49:04 pm
content: Quote from: FileNotFound__ on May 15, 2022, 04:32:33 pm

author: Simon
author_rank: Unknown
timestamp: May 15, 2022, 05:11:46 pm
content: Quote from: BBBbbb on May 15, 2022, 03:28:18 pmIf the average price of a PSU is £20 and you bey one for £5 you are a fool, if you pay £40 for one you should be able to expect it to be decent. In my case I have never had issues and I am genuinely surprised that this PSU is the only component remaining of the first PC I built here in the UK when I moved back in 2007! so it's at least 12 years old and I had it running a decent CPU and GPU, infact as I protein fold the whole system runs full power all the time.I only recently changed it as I fancied a modular one for less wiring and was changing most my PC parts so actually ended up just taking all the old stuff out of the case to keep as a backup/test system or I'd still be using the same "puny" 400W PSU

author: Bud
author_rank: Super Contributor
timestamp: May 15, 2022, 06:49:11 pm
content: It is hard to overvoltage computer switching power supplies, even the very old ones. On 5V rail you may get only 6V or something. On 12V rail you may squeeze out 15V maybe if you try hard. It is easier to lower the voltage than to raise it, even with that there are limits that a particular PSU can provide.

author: strawberry
author_rank: Super Contributor
timestamp: May 15, 2022, 07:08:38 pm
content: seen some desktop motherboard that wont boot without PSU handshake. PSU supervisory controller went bad first(corrupted memory..)

author: mapleLC
author_rank: Frequent Contributor
timestamp: May 16, 2022, 08:24:17 am
content: Quote from: Stray Electron on May 15, 2022, 01:29:48 pmNever underestimate the power of confirmation bias.

author: wraper
author_rank: Unknown
timestamp: May 16, 2022, 11:23:32 am
content: Quote from: strawberry on May 15, 2022, 07:08:38 pmThere is no "handshake". And properly designed motherboard is not supposed to boot before PSU sets "power-good" signal high.

author: wraper
author_rank: Unknown
timestamp: May 16, 2022, 11:30:03 am
content: Quote from: Bud on May 15, 2022, 06:49:11 pmIt's not hard but very easy to output a voltage much higher than numbers you mentioned as of SMPS itself. The only thing that makes it non trivial if you want to do so is that any non garbage ATX PSU made these days has a supervisor circuit which will shut it down once OVP protection triggers.

author: Shock
author_rank: Super Contributor
timestamp: May 16, 2022, 05:00:03 pm
content: You should just leave it at I brought XYZ, and this is my failure analysis.There are hundreds of PC power supply brands and 95% of them aren't worth buying when you consider a failure or a surge can take out your supply/board/ram/cpu etc.This is not a problem that needs a solution it's been like this for 30 years or more? They make em cheap on purpose, noone cares unless you are a sucker and buy a pc with a dirt cheap power supply and get told later you brought trash.Edit:A realistic formula would be 20% of motherboard/cpu/ram cost. But if you are buying a decent GPU or a lot of storage you're getting a good power supply no matter what. Never spend $60 and run $2000 of gear off it, that is just asking for it. I also don't like buying mainland chinese products, Taiwan has much more experience in this area. Don't buy parts from companies that don't have websites unless you consider them disposable parts as it's probably some other rubbish brand relabeled anyway.