Hey mate :) That PSU is either broken or out of spec because its an ancient design and cross-loaded. A-tier modern supplies are consistently under 20mV p-p.

I watched a ton of your videos yesterday, and first and foremost, I loved them. Lots of good and interesting content. I wasn't able to find the follow up video to this if you ever made on testing a newer, better PSU. I am about to embark on making a bench top from a Seasonic (eww) 750w PSU (Seasonic SSR-750FX 80 plus gold) and I notice that in the very bulky 24 pin ATX motherboard cable, there are capacitors that clean up the ripple. Just wanted to come back and share that with ya! Keep up the good work!

You usually use bench power supply if device itself don't have linear regulator or DC/DC converter. Also it seems that ATX psu violates specs. 12V should have max 120mV ripple. Maybe that psu is older models that need also some load for 5V line. New ATX create 12V and then use DC/DC to do 5V and 3.3V

Hi Thank you for the video. Can you try the same test on another ATX power supply please? And one where you load the 5volt line when you checking the 12 volts output

Put a load on that ATX PSU and than check the ripples, normally in PC there is constant current draw for motherboard, harddrive gpu and than the regulation is much better. Other thing is that you use ATX and bench PSU in different ways, bench is designed to have low ripples so you can directly power your microchips. In PCs 12V is always used to drive motors (which doesn't need to be well filtered) or stepped down in peripherals to 5V, 3V or even 1,5V so proper filtering is done on that voltages. You Know that 12V is not powering directly any chips. 5V and 3V rails in ATX should have lower ripples.

Is it true if you connect all 12 volt yellow wires into one lead will give you the total amps in atx power supply? Example the rating listed is 14 -20 amps on a 350 watts atx ps. I want to use it in electrolysis to remove rust and it needs higher amps on a 12 volt dc

I have a bunch of different ATX-PSUs and most of them perform pretty well? Is your ripple under a certain load? Some old ATX need some rails loaded to work properly, typically at least .5 or better 1 Amps at least. Many of mine ATX have around 50...150 mV ripple - thats fine for many applications. Its not a linear regulated bench PSU of course.

Is it safe to put a scope on an at power supply? Are they isolated? Also, I'm interested to test my high end at psu. It's a platinum rated supply, about a 450 dollar psu

i have a 5v power supply i have questioned for awhile. it burns out my tp4056 often yet a charger right next to it built the same using an atx converted supply never burns out a chip and is running at high voltage. is there a module that would help clean up my dc power supply? im willing to spend a little just to test the theory at this point. its become kind of a project lol

The same goes for Amateur radio operators, there are a few that use ATX supplies but as soon as you really push output power then they just fall over. Also not the greatest to power LiPo Chargers for drone batteries. Been there done that

Does the desk multimeter go to standby all the time? I heard people complain about that

Just stick a big capacitor across that ATX output, job done

Interesting. However it can be easily controlled using some bypass capacitors, almost all internal PC hardware must have some form of smoothing power intake Circuitry to overcome this.

Sorry but it is unfair to test such a cheap ATX PSU without comparing your expensive Bench PSU with a 80 Plus Certified ATX PSU (what we normally use for gaming and as an alternative for a bench PSU) they are also affordable and very high quality. I tested mine (80 Plus Platinum certified) that I bought on Ebay for just $40 and it is very clean. Perhaps not exactly as an expensive Bench Power Supply but very similar for the price. You mentioned Thermaltake... the brand is irrelevant when talking about the quality of a PSU. At the end the certification is what is important because they need to have way better parts and components to pass each level of the certification. Thermaltake for example has cheap and low quality PSUs too, unless they are 80 plus certified and each level of 80 plus is night and day difference between Bronze and Titanium certifications.

It has to be a really crappy ATX PSU if the 12V rail has undervoltage on it even without a load. I'd throw away the cheap Chinese breakout box, too, and connect the PSU's own wires to bus bars, etc. The 24pin MoBo-cable has very limited current carrying capabilities compared to grouping all the rail and ground wires in separate bundles and soldering them to hefty lugs. I'm building one at the moment using a basic 2007 460W HP unit and all the GND wires bunched together are thicker than my thumb. The Molex-boxes are for testing and repairs, not power delivery.

You must remember that a PC PSU isn't designed to be bench top power supply anyway, that's just a hack, a really nice cheap one too, not bad for less than half a volt :) I noticed that at no stage did you compare prices, you can make a super one for a tenth of the price and you should clean the power first like it would be if it was plugged into a pc, those would normally be plugged into a UPS or an inverter, not directly into the wall 😇

Do I see that correctly that your ripple is at 60Hz? kzfaq.info/get/bejne/nL6baaugydq3nYU.html That cannot come from the ATX power supply because Switch Mode Power Supplies work at a much higher frequency. 60hz is picked up by the scope, typically by a bad or missing shielding on the test probes. i could be wrong,... but 60Hz and an SMPS? that doesn't add up... /ChriV

A bit late to the party, what you could do if you want to clean up the output of an ATX PSU, you can add a chock, (make sure it can handle the current though) and then another filter cap thereafter to that output, it does clean it up quite a bit depending on what you use, still does not clean up totally..... ATX is not a good bench top PSU for development or testing...

Junkie power? My ATX is as solid as a rock and clean as heck...Ripple is as low as can be given its purpose (max 30mV) Logic, because CPU's tend not to like ripple... Problem, most of the times is that ATX PS's used for this are almost always OLD. Most problems occur with older smoothing caps. ...BTW..Also, LIMIT your BW on the scope....Way cleaner results with these scopes.

You shouldn't compare DIY bench power supply from old atx to a well manufactured bench power supply🥴

Basically…….it aint worth the hassle making a bench PSU from an ATX.