ATX 700w corsair psu making noise GS700 - Page 1
Forum section: electronics / beginners

author: davidut5
author_rank: Contributor
timestamp: March 29, 2023, 10:17:00 am
content: A friend gave me a faulty corsair GS700 700w power supply, it was not opened before. I saw two bulging capacitors on 5vsb and on fan control, replaced all electrolitics on the board with new quality ones(except bulk cap, measured ok). Anyway the power supply makes a lot of hissing, popping noises, especially with no load just green wire to ground. The no load noises are concerning, if i put some load anywhere say 1 amp the concerning noises disappear and remain a rather abnormal hissing.When tested on a system, when pc is starting up it makes a lot of noise, when hdd is loading os.The noise comes from main transformer. When the unit is warm, if i press hard on the transformer in the middle the noise almost disappears.All voltages are good, pc runs fine under load, even tested with some 12v light bulbs and it was fine at 40A on the 12v for about 10minutes.The pfc/pwm controller is cm6800t, the secondary rectification is with transistors, the 3v3 and 5v are done with dc-dc converters.Got a little dso pro scope, but dont really know what to see, and where to look for, and most important how its supposed to look like.Found a lot of similar units online with the noise problem, and with burning 12v toroid inductor coil. On the unit i have, the 12v inductor is getting a little hot with minimal load. This could be a bad design.Turns out it is easier to repair units that have no life, than the ones that work.I put a wire around transformer to get some readings, in the pics below.https://youtu.be/uCE4kdqoj_s

author: wraper
author_rank: Unknown
timestamp: March 29, 2023, 10:24:56 am
content: QuoteProbably transformer core halves came apart of core is loose within the bobbin. You could either take it apart if its really does not hold together after removing green tape or just fill the gaps with adhesive if it does not come apart. First check if there are no issues with solder joints though.

author: RoGeorge
author_rank: Super Contributor
timestamp: March 29, 2023, 12:13:50 pm
content: Working without any load means very short PWM pulses, might be quite stressful for a SMPS designed to deliver hundreds of W. If all the voltages are good, connect it to the MB, and the hissing should go away.Does it still hiss when connected to the PC?

author: davidut5
author_rank: Contributor
timestamp: March 29, 2023, 12:25:08 pm
content: Tested other 450w,500w,650w psu, just green wire to ground and no noise. The 650w i think has the same controller cm6800t.When connected to pc it makes the hissing sound, and cliks/pops consistent with hdd accessing os, as i have said. So dynamic load makes it sound worse.https://youtu.be/vWqsKOgwOJ4

author: Vovk_Z
author_rank: Super Contributor
timestamp: March 30, 2023, 05:30:52 am
content: Some ATX PSU types are prone to hissing. I would sell it to somebody who doesn't care about a sound (with a proper describing).

author: davidut5
author_rank: Contributor
timestamp: March 30, 2023, 09:11:27 am
content: If it was just the hiss, probably normal on low tyer units but the squeaking/clicking is not ok, see video on the end, in reply3.

author: agehall
author_rank: Frequent Contributor
timestamp: March 30, 2023, 07:50:16 pm
content: I’m not sure is I’m just unlucky or if Corsair makes terrible PSUs - I’ve had 3 different ones from them that all suffered from horrible coil whine. All returned. I suspect OP might have found another unit from them that is bad.

author: davidut5
author_rank: Contributor
timestamp: March 30, 2023, 07:59:10 pm
content: GS series was not top of the line from corsair, with samxon capacitors. They have a lot of garbage psu, the ax, hx are/were the best. Like any other, they have good and bad units to cover the market.

author: MathWizard
author_rank: Super Contributor
timestamp: March 31, 2023, 09:21:57 pm
content: Is any of the noise just from the fan ?? I would not like hissing/popping sounds what ever it is.Of the few Corsair PSU's I've tested/worked on, or used, only 1 had any amount of hiss/coil whine. Makes me worry some cap is about to explode.

author: davidut5
author_rank: Contributor
timestamp: March 31, 2023, 10:01:57 pm
content: Not the fan, that is another matter.When it warms up, the noise gets lower to the point that pressing the transformer core does not alter the noise. Could be transformer fault, i really don't want to try and disassemble it if I'm not sure. I'm afraid it would come apart in pieces. If it would have the air gap just a hair smaller probably the noise would go away, or it could be some instability in the loop, some component lost its value, not capacitors, those i ruled out(except smd ones).

author: MathWizard
author_rank: Super Contributor
timestamp: March 31, 2023, 11:06:08 pm
content: I've had a few GPU's with annoyingly loud coil buzz/cap buzz, not when idling tho, just in games. IDK if adding more of the caulking they use, helps or not. Then there's thermal issues with adding that stuff in some places.I haven't taken apart a SMPS transformer in many years. I'm guessing they are hot-dipped in insulation coating. And basically very hard to take apart without ruining something.The loudest buzzing 750W PSU that I have, one of these days I should swap in and out a few parts, from other 750W Corsair's I have taken apart. Maybe with a rolled up tube of paper, I could hear what part does it.I would like to use a mic, and on a scope, see what part(s) make the sounds at start up and turn off, that sounds like a relay. Is it all the inductors, or the boost converter inductor? or the main switching inductor ??

author: davidut5
author_rank: Contributor
timestamp: April 01, 2023, 07:24:41 am
content: There is actually a relay on better models, to bypass thermistor after startup.

author: beatman
author_rank: Regular Contributor
timestamp: April 02, 2023, 07:57:34 am
content: i have 24v 20A led smps with noisy transformer i just give a good portion of hot glue and the noise disappear to 2/3

author: davidut5
author_rank: Contributor
timestamp: April 02, 2023, 09:32:16 am
content: I did that, no improvement. Then i realized it was wrong and tried to remove it. The unit is fanless up to a point, so the transformer gets quite hot and the glue melts, leaking all over, so not a good idea.

author: wraper
author_rank: Unknown
timestamp: April 02, 2023, 10:04:51 am
content: Quote from: beatman on April 02, 2023, 07:57:34 amQuote from: davidut5 on April 02, 2023, 09:32:16 amJust wow, real stupid suggestion and even stupider actually following it. Now you won't be able fix it with something decent as now everything is covered with that soft/liquid (depending on temperature) garbage.

author: beatman
author_rank: Regular Contributor
timestamp: April 02, 2023, 12:01:01 pm
content: ok you have to check first of all how hot this thing run like i do.to my problem was ok the smps runs without problems the transformer does not run very hot and hot glue stay in tact.of course i apply differend glue material for higher temp.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 02, 2023, 02:07:30 pm
content: It could be fun and educational for fix it but I would simply toss it. I would never try to repair a computer power supply that can be replaced relatively inexpensive.

author: davidut5
author_rank: Contributor
timestamp: April 02, 2023, 06:58:46 pm
content: For fun i do this, i like fixing stuff.Got another faulty corsair cx750 750w unit, from what i see online internals are the same. Hopefully i can swap parts and see what is wrong with the gs700. Of course, in the end fix them both!

author: davidut5
author_rank: Contributor
timestamp: April 07, 2023, 05:35:50 pm
content: Ok, so replaced the transformer from the cx750 and the no load noise is gone, the system starting up noise is about 50% quieter, and it does not change with temperature or pressing down on the core.This is most likely a manufacturer problem and i have no faulty part to replace.Problem with this cwt puq series is noise and 12v inductor burning, so definitely something wrong with all of them.

author: davidut5
author_rank: Contributor
timestamp: May 01, 2023, 11:45:48 am
content: My aliexpress order arrived with the parts to fix cx750, st-by pwm ic OB5269CP and power mosfet CEF04N7G plus some resistors. I was disappointed to hear the same noise as GS700.This is the end of me trying to figure out the source of the problem.

author: tunk
author_rank: Super Contributor
timestamp: May 01, 2023, 12:51:19 pm
content: Seem to remember that the ATX specs says max allowed ripple onthe 12V rail is 120mVpp. Also, I think ripple is measured witha 20MHz filter, and your DSO Pro has a claimed 5MHz bandwidth,so it won't see the maximum peaks.