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PSU ripple...acceptable?

post #1 of 15
Thread Starter 
Okay, so here is a little backstory to the PSU in question:

-It's a BeQuiet Systempower 700W
-it's from 2008

-It had blown output capacitors on the 5V rail which I replaced in ~2012 as the PC wouldn't boot reliably anymore.
-The same symptoms started developing again in ~2014 so I went ahead and recapped the whole thing with Panasonic FR.
-The PSU has worked fine since except that the PC randomly fails to boot when overclocked (happens once a month or so).

Today I decided to use my tiny Oscilloscope and take a look at the ripple on the 3.3, 5 and 12V rails. My equipment is far from ideal and it was somewhat difficult to include both switching and mains noise in my result but I think I managed to get a relatively accurate estimate of the ripple.

3.3V: 40mVpp
5V: 90mVpp
12V: 150mVpp

It seems both the 5V and 12V rails are out of ATX specification.mad.gif
I also tried botching a large low esr cap to the 5V rail, which cleaned the output ripple to 60mVpp.

So what do you think? Would it be ok to leave the PSU as it is or should I do something about it? I could simply add more output capacitance to the 5 and 12 volt rails but there must be a maximum output capacitance specification for computer powersupplies, right? After all I don't want to screw up the whole PC because of a crappy PSU. And besides, the PSU seems to be a real cap-killer - I haven't looked inside but I could bet it has done some damage to the output caps again.rolleyes.gif
post #2 of 15
There is no way in hell those ripple results are okey the 12v and 5v are way out of ATX specifications.
Sory but it needs to go in a dumpster.
Edited by shilka - 6/10/16 at 8:34am
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post #3 of 15
Thread Starter 


That's the 12V rail...so the dumpster it is, then?
If it needs to go, then it'll go, it's done it's job for long enough...smile.gif

I've had a quick look at a possible replacement PSU but am a little unsure about wattage. This PSU has 700w but it was originally powering a gtx295 which I have swapped for a gtx770. My rig:

-i7 920 @ 4Ghz
-GTX770 (possibly GTX970 in the future)
-two 7200rpm hdd's + one SSD
-Corsair H80i liquid cooler

Do you think I could manage with a slightly lower powered (600W), good quality PSU? I refuse to buy another crap PSU so I've excluded everything not Seasonic from my search. For example the Seasonic S12II-620 would fit nicely into my budget if it is powerful enough.
post #4 of 15
Quote:
Originally Posted by 12Vpp View Post



That's the 12V rail...so the dumpster it is, then?
If it needs to go, then it'll go, it's done it's job for long enough...smile.gif

I've had a quick look at a possible replacement PSU but am a little unsure about wattage. This PSU has 700w but it was originally powering a gtx295 which I have swapped for a gtx770. My rig:

-i7 920 @ 4Ghz
-GTX770 (possibly GTX970 in the future)
-two 7200rpm hdd's + one SSD
-Corsair H80i liquid cooler

Do you think I could manage with a slightly lower powered (600W), good quality PSU? I refuse to buy another crap PSU so I've excluded everything not Seasonic from my search. For example the Seasonic S12II-620 would fit nicely into my budget if it is powerful enough.

600W easily handles what you have. It is much better to have a high quality PSU as you don't want random reboot or worse yet, fried your new GTX 970.
post #5 of 15

Yeah, destroy that PSU. Get rid of it. Make sure no one could accidentally find it and decide to use it. It's not a PSU, it's a death wish for a computer. It should never have been made. heh

 

Anyway, your computer's power draw is so low now that you could easily power it with a good quality-made 450W PSU. The GTX 970 pulls even less power, so there you go.

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post #6 of 15
The Seasonic S12II is group regulated which means its voltage regulation is not all that great, this is the reason for the low price.
its better then most other group regulated units such as the Corsair CX but its still group regulated, if you can live with that then its a cheap option.
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post #7 of 15
Thread Starter 
Well if I can go even lower than 600w, then that opens up a whole lot of possibilities for me. For example the Seasonic G550, which I could get a good deal on. That's a newer, not group-regulated design, right?

Seriously though, what wattage exactly should I be looking for? 450W seems tiny to me. The stone-aged i7 @4Ghz is a power hog and I want to have some headroom for overclocking as well.
post #8 of 15
The power draw of the system you have is about 300-350 watts at full load with OC, so yes a 450 watt PSU could power your system with no problems.
Units below 500 watts are just way overpriced so my advice is get a good 550 watt PSU.

Is the Corsair RMx the EVGA SuperNova G2 or the XFX XTR available at prices you can afford?
If not then the Seasonic G is good option.
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post #9 of 15

Yeah, and the GTX 970 just SIPS power. Then if you get a new CPU, like a 6600K or 6700K, your power consumption will drop even further. 450W isn't "tiny", especially not for your rig. However, with PSU prices the way they are, you'd be better off buying a 550W+ PSU. It's kind of like hard drive pricing, there's a sweet spot, and that sweet spot is kind of at 650W/750W/850W PSUs right now with some 550W PSUs still seeing good deals.

It's a computer!
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250 GB Samsung 840 EVO (OS) 3 TB Toshiba P300 (storage) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
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Thermaltake Frio Win 7 Home Premium x64 SP1 Retail AOC G2460PG (24" 1920 x 1080 144Hz G-SYNC) Filco Majestouch 104-key Cherry MX Blues w/NKRO 
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Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
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It's a computer!
(18 items)
 
  
CPUMotherboardGraphicsRAM
i5-2500K @ 4.5GHz (1.368-1.384V fixed voltage) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
Hard DriveHard DriveOptical DriveOptical Drive
250 GB Samsung 840 EVO (OS) 3 TB Toshiba P300 (storage) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
CoolingOSMonitorKeyboard
Thermaltake Frio Win 7 Home Premium x64 SP1 Retail AOC G2460PG (24" 1920 x 1080 144Hz G-SYNC) Filco Majestouch 104-key Cherry MX Blues w/NKRO 
PowerCaseMouseMouse Pad
Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
AudioAudio
X-Fi Titanium HD Klipsch ProMedia 2.1 (with 16 AWG Monster Cable... 
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Reply
post #10 of 15
Thread Starter 
Okay, thanks for the suggestions!
I tried stressing the PC as hard as I could (while keeping an eye on my fishy PSU rolleyes.gif) and measured the power draw from the socket. It peaked at around 600w. Assuming n = 0.8 (optimistic), the power draw from the PSU would've been around 480w, which sounds reasonable. A 550w PSU seems to be a good fit so I think I'll order the G550. It's 25-50€ cheaper than the Corsair, XFX and EVGA and seems to be just as good as those.thumb.gif
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