How to test a 1200W ATX power supply ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 03, 2018, 01:29:26 am
content: I have a huge broken PSU on the way to try and fix, I sure hope I can do something with it if not. I have no idea what's going to be wrong with it.My computer probably never goes over 400W. So if there's something wrong at higher loads I won't be able to really test it.The 12V single rail is rated for 100.4 Amps, I would need an awful lot of 1/4W resistors LOL.Any ideas ?

author: edpalmer42
author_rank: Super Contributor
timestamp: May 03, 2018, 01:58:14 am
content: Lots of car battery testers have a fixed load of 100A. Fancier variable ones go up to 400A or 500A.

author: james_s
author_rank: Super Contributor
timestamp: May 03, 2018, 03:14:05 am
content: You probably don't need to load it down fully to be reasonably confident that it's working. Automotive light bulbs can be decent test loads, conventional headlamp bulbs are 55/60W. You can light both the low and high beam filaments at once to get a 115W load per lamp.

author: james_s
author_rank: Super Contributor
timestamp: May 03, 2018, 05:35:51 am
content: I thought of suggesting that, but with DC the plates will rust away very quickly, become less conductive and overall make a huge mess. Salt water works well with AC though, at one time it was common to make inexpensive rheostats for theater lighting using barrels of salt water. I've heard of it being used as a test load for generators too.

author: tron9000
author_rank: Frequent Contributor
timestamp: May 03, 2018, 08:14:17 am
content: Alot of 3AWG wire in bucket of water? or a kettle hooked up to an inverter maybe? You'd need a beefy shunt(0.01) fro 1V/100A or a clamp meter to measure current.but first things first...does it turn on? Get an ATX tester like this:ATX power supply tester

author: BrianHG
author_rank: Super Contributor
timestamp: May 03, 2018, 09:08:27 am
content: 1kw of light @ 12v for 8$, purchase 2 sets:https://www.amazon.com/SODIAL-LAMP-BULB-HEADLIGHT-WHITE/dp/B00LGJ4SRU/ref=sr_1_2?ie=UTF8&qid=1525337387&sr=8-2&keywords=12v+100w+bulbYou will need a log of good wiring. You may also check current draw on 1 lamp and multiply by the number of lights.As for lower voltages, like 5v, you will need many more, however, halogen's resistance really drops when you drive them dimly.Or, better regulated for 5v & 3.3v, well, wire of huge resistors may be a better fit, choose from multiple gold ones in parallel and series and you will need a heat sink: (Larger resistors exist, but, they are 40$ and above and don't go so low in resistance)https://www.digikey.com/products/en/resistors/chassis-mount-resistors/54?k=power+resistor&k=&pkeyword=power+resistor&pv174=26&FV=8000e%2Cmu1+mOhms%7C2085%2Cmu1+Ohms%7C2085%2Cmu1.333+mOhms%7C2085%2Cmu10+mOhms%7C2085%2Cmu100+%C2%B5Ohms%7C2085%2Cmu100+mOhms%7C2085%2Cmu110+mOhms%7C2085%2Cmu15+mOhms%7C2085%2Cmu150+%C2%B5Ohms%7C2085%2Cmu150+mOhms%7C2085%2Cmu166.7+%C2%B5Ohms%7C2085%2Cmu167+%C2%B5Ohms%7C2085%2Cmu2+mOhms%7C2085%2Cmu2.5+mOhms%7C2085%2Cmu20+mOhms%7C2085%2Cmu200+%C2%B5Ohms%7C2085%2Cmu200+mOhms%7C2085%2Cmu220+mOhms%7C2085%2Cmu25+mOhms%7C2085%2Cmu250+%C2%B5Ohms%7C2085%2Cmu250+mOhms%7C2085%2Cmu270+mOhms%7C2085%2Cmu3.333+mOhms%7C2085%2Cmu300+%C2%B5Ohms%7C2085%2Cmu300+mOhms%7C2085%2Cmu330+mOhms%7C2085%2Cmu333+%C2%B5Ohms%7C2085%2Cmu375+%C2%B5Ohms%7C2085%2Cmu390+mOhms%7C2085%2Cmu400+%C2%B5Ohms%7C2085%2Cmu41.7+%C2%B5Ohms%7C2085%2Cmu430+mOhms%7C2085%2Cmu470+mOhms%7C2085%2Cmu5+mOhms%7C2085%2Cmu50+%C2%B5Ohms%7C2085%2Cmu50+mOhms%7C2085%2Cmu500+%C2%B5Ohms%7C2085%2Cmu500+mOhms%7C2085%2Cmu62.5+%C2%B5Ohms%7C2085%2Cmu680+mOhms%7C2085%2Cmu750+%C2%B5Ohms%7C2085%2Cmu820+mOhms%7C2085%2Cffe00036%2Cfffc06b0%2Cfffc0112%2Cfffc02e2&quantity=0&ColumnSort=2085&page=1&stock=1&nstock=1&pageSize=25

author: BrianHG
author_rank: Super Contributor
timestamp: May 03, 2018, 09:15:11 am
content: 300watt, 0.1 ohm, 0.22 ohm, 0.33, ect,https://www.aliexpress.com/item/RX24-300W-0-1R-0-1RJ-0-1OHM-300W-Watt-Power-Metal-Shell-Case-Wirewound-Resistor/32636640475.html?spm=2114.search0104.3.116.39ba39e63bytwY&ws_ab_test=searchweb0_0,searchweb201602_3_10152_10065_10151_10344_10068_10130_5722815_10342_10547_10343_10340_5722915_10548_10341_10698_5722615_10696_10084_10083_10618_10139_10307_5722715_5711215_10059_308_100031_10103_10624_10623_10622_5711315_5722515_10621_10620,searchweb201603_25,ppcSwitch_5&algo_expid=214855ff-bd0c-49e8-a36a-5b27f432fe34-18&algo_pvid=214855ff-bd0c-49e8-a36a-5b27f432fe34&transAbTest=ae803_1&priceBeautifyAB=0500watthttps://www.aliexpress.com/item/RX24-500W-0-5R-0-5RJ-0-5OHM-500W-Watt-Power-Metal-Shell-Case-Wirewound-Resistor/32636032411.html?spm=2114.search0104.3.22.12d451c6LvgywT&ws_ab_test=searchweb0_0,searchweb201602_3_10152_10065_10151_10344_10068_10130_5722815_10342_10547_10343_10340_5722915_10548_10341_10698_5722615_10696_10084_10083_10618_10139_10307_5722715_5711215_10059_308_100031_10103_10624_10623_10622_5711315_5722515_10621_10620,searchweb201603_25,ppcSwitch_5&algo_expid=3c51b36d-6ef2-4f20-a18d-7e27b234a5ed-3&algo_pvid=3c51b36d-6ef2-4f20-a18d-7e27b234a5ed&transAbTest=ae803_1&priceBeautifyAB=0When buying a heatsink, remember you will want to be able to dissipate 2kw, and add a huge 12v fan on the heatsink, you will warm up a room in your home with this full load.Don't forget thermal transfer paste or pads.

author: Zero999
author_rank: Super Contributor
timestamp: May 03, 2018, 09:24:43 am
content: Be careful, it's unlikely the power supply will be able to supply 1200W continuously. It's most likely its peak rating.

author: BrianHG
author_rank: Super Contributor
timestamp: May 03, 2018, 10:20:52 am
content: In other words, don't use for dedicated bitcoin mining hardware which loads the 1.2kw continuous...

author: edpalmer42
author_rank: Super Contributor
timestamp: May 03, 2018, 03:32:15 pm
content: It always makes me nervous to read messages where people recommend light bulbs as load resistors. Have you ever measured the cold resistance of a light bulb - regular or halogen? It's extremely low compared to the resistance under normal operating conditions. That means that your power supply will see a huge current spike when you connect the load. It could easily be 10 times higher than the normal load. If the load is connected when the power supply is turned on, the supply could refuse to start or it could even be damaged.I never use or recommend light bulbs as load resistors. It's just not worth the risk.Ed

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 03, 2018, 04:21:09 pm
content: Quote from: Hero999 on May 03, 2018, 09:24:43 amYeah for sure, and it's 1200W recommended max across all rails, even tho the 12Vx110.4A=1204.8WI've order some 50A current shunts. Although that's just resistive loading, I'm not buying a proper load tester any time soon.I should have done some homework before ordering this broken Corsair AX1200W. Sure hope whatever's wrong is not some part I can't find a datsheet for let alone order. Or that the SMD soldering is above my skill/equipment level.Oh well, it's an investment. I've already got some of the datasheets from the names in johnnyguru's reviews.

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 03, 2018, 04:25:49 pm
content: Quote from: Hero999 on May 03, 2018, 09:24:43 amIf it's a crap PSU it's likely to be the peak rating, if it's a decent one it's what it can supply continuously. It's one of the ways you can distinguish fair quality from rubbish in the PSU department.

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 03, 2018, 04:35:02 pm
content: Nah it's 1 of the best gold rated (at least when it released), I think that's 90% efficiency so 1333W at the wall. But yeah that's short term peaks I guess.With the wattage of even tops GPUs dropping so much the last few years, it's over sized even for most people with 3-way CF/SLi

author: edpalmer42
author_rank: Super Contributor
timestamp: May 03, 2018, 05:07:17 pm
content: Quote from: lordvader88 on May 03, 2018, 04:21:09 pmHow is a 50A shunt going to help you? All that means is that you can pass 50A through the shunt. It doesn't mean that it's a 50A load.Ed

author: Mr. Scram
author_rank: Super Contributor
timestamp: May 03, 2018, 05:18:23 pm
content: Quote from: lordvader88 on May 03, 2018, 04:35:02 pmAgain, decent ones will do that continuously. Only the crap ones rate peak performance.It's a little more nuanced than that as different rails are rated differently, but the rating should be the actual continuous performance. The good ones do that and then some.

author: dnwheeler
author_rank: Regular Contributor
timestamp: May 03, 2018, 07:46:34 pm
content: Quote from: lordvader88 on May 03, 2018, 04:35:02 pmThe bronze, silver, gold, platinum and titanium ratings are simply efficiency ratings. They say nothing about quality or power ratings.

author: james_s
author_rank: Super Contributor
timestamp: May 03, 2018, 09:09:45 pm
content: I've never had any trouble using light bulbs as test loads on power supplies. The inrush is only milliseconds and most supplies are able to cope with it. Worst case something like this will shut down if you try to power it up into an excessive load.

author: Cliff Matthews
author_rank: Unknown
timestamp: May 03, 2018, 10:26:37 pm
content: Tungsten bulb filaments have low cold resistance, often just 3 or 4 of them will cause the supply to falsely detect a short. *edit -you could pre-heat them with series 22 ohm power resistors that you can later bypass, but that still doesn't load the 5v rails.The cheapest load to briefly test ATX supplies is likely Nichrome wire from old portable hair-dryers, cut-up and inserted into heat resistant barrier strips bolted onto a piece of plywood covered in stapled tin-foil (stretch-out nichrome wire with nails). Many hair dryers have two coiled segments, each ~21 ohms, so there's enough for 12 x 3.5 ohm cuttings. These each can be folded and inserted into the barrier strips as two resistors of 2.5 and 1.0 ohms.This tests each Molex at ~80watts, which is near the limit of most PC wiring. Of course a fan would help and this is definitely not for unattended use..

author: KE5FX
author_rank: Super Contributor
timestamp: May 03, 2018, 10:36:59 pm
content: You could monkey around with salt water and mops and whatever, or buy some expensive automotive light bulbs, or you could just buy a couple of cheap 100-foot extension cords and use them to short out the supply. When you want to dissipate 1200 watts, the only thing that really matters is mass.

author: BrianHG
author_rank: Super Contributor
timestamp: May 03, 2018, 11:03:07 pm
content: Quote from: KE5FX on May 03, 2018, 10:36:59 pmThis costs more than 15$ for 2kw of automotive head lamps from Amazon.However, when you say cheap, you must then mean 2-3$ 100 foot extensions. I don't know if they come that cheap...

author: Cliff Matthews
author_rank: Unknown
timestamp: May 03, 2018, 11:14:40 pm
content: On the extension cord.. it would be difficult to feed power into it, since each Molex has typical 7amp wiring. You still require a ton of female Molex' to solder to it. Might work.. 1 conductor for 5v and 2 for 12 v I can smell the BBQ already.. I prefer nichrome wire screwed into barrier strips.

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 04, 2018, 02:25:51 am
content: Quote from: edpalmer42 on May 03, 2018, 05:07:17 pmright, right

author: ejeffrey
author_rank: Super Contributor
timestamp: May 04, 2018, 03:09:55 am
content: ++ on the nichrome wire. It is cheap, can easily be combined into convenient resistances, and can handle a lot of power as long as you don't mind it getting hot. You can tear it out of a hairdryer or toaster, or you could just buy some.

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: May 04, 2018, 03:18:37 am
content: Quote from: james_s on May 03, 2018, 09:09:45 pmTrue if the power supply is working correctly. But it's a faulty unit, so the OP can't guarantee it will shut down correctly (or at all).

author: edpalmer42
author_rank: Super Contributor
timestamp: May 04, 2018, 03:35:14 am
content: Quote from: thermistor-guy on May 04, 2018, 03:18:37 amOh, it'll shut down all right, but maybe not in the way you'd like.Ed

author: 0db
author_rank: Frequent Contributor
timestamp: May 24, 2020, 02:33:54 pm
content: +1.Great topic

author: jeroen79
author_rank: Frequent Contributor
timestamp: May 25, 2020, 12:19:57 am
content: Quote from: ejeffrey on May 04, 2018, 03:09:55 amI was thinking about that too.Use two parallel metal bars/tubes as bussbars and then wrap the nichrome wire back and forth between them until you get the desired current draw.

author: jeroen79
author_rank: Frequent Contributor
timestamp: May 25, 2020, 12:26:25 am
content: Quote from: edpalmer42 on May 03, 2018, 03:32:15 pmWhat if you use several bulbs and turn them on one by one?

author: KE5FX
author_rank: Super Contributor
timestamp: May 25, 2020, 04:53:09 am
content: Meh, I doubt a light bulb is much harder on the supply than several thousand microfarads of low-ESR bulk capacitance on the motherboard it's intended to drive.