Seasonic ss-520gb 520 watt voltage drop and bad voltage regulation

[Quaddro]

i have a seasonic psu model seasonic ss-520gb, with drop voltage and bad voltage regulation

Measure with digital multimeter,
Load using my trusty dummy motherboard and 3 hard drive:
12v rail give 11.35-11.55v with (very) rapid changing.
And same thing with the other rail.

But if no load, shorting green and black cable, it can provide up to 11.85v.

--
What about the dummy? maybe this one cause error.
Nope, i've already tested this dummy (motherboard+hdd) with other psu, and still give strong 12v voltage
--

All caps is japanese. physically check, all non bulging caps.

I've checked the component in primary and secondary, change tl431 ic, all 3 optocoupler, primary and apfc mosfet and supervisor ic (HY-51n), even i've tried to replace main transformer from other same psu, but still no luck.

can bad cm6800g cause this issue?
or bad capacitor in secondary?
or maybe any other advice..

Thanks alot for the enlightenment..

[Quaddro]

Re: Seasonic ss-520gb 520 watt voltage drop and bad voltage regulation

Eureka !!

i was almost give up..
And for the last effort, i've replace all secondary capacitor, and voila the voltage regulation back to normal.
12v rail give me 11.9v all the time even with the high load.

It's should be an easy fix if it using second tier of capacitor (teapo, ost etc)
But it's harder because (maybe) some japanese capacitor not bulged when failed.

[Wester547]

Re: Seasonic ss-520gb 520 watt voltage drop and bad voltage regulation

OST and Teapo are actually notorious for failing without visible signs. That said, I’m surprised the culprit were the NCC caps - it looks like they used good series (KZE, KY, KZH, or something similar?) on the secondary side (and I doubt they are counterfeits unless the bungs are wrong, but I don’t think Seasonic would use fakes). I’d guess the unit runs rather hot for them to have dried out over time and cause problems (it doesn’t look like there’s ample room for airflow and I see the caps located near diodes, coils, and heatsinks - all components which can dissipate a significant amount heat, especially with an inept fan controller). Maybe the capacitance had fallen over time too, which also may be responsible for the sagging output voltage. I believe high leakage current can cause this too.

Going by the datecodes I can see on the caps and on one of the transformers, it looks like they were made around 11-12 years ago or so. So I guess it’s not a bad life, despite falling under the 15 year max life spec most manufacturers rate their caps at (but that’s if you keep them cool).

[Stefan Payne]

Re: Seasonic ss-520gb 520 watt voltage drop and bad voltage regulation

That said, I'm surprised the culprit were the NCC caps - it looks like they used good series

That unit is more than 10 years old.
Low End unit, cost down from the real S12II, wich had dual mag amps...

Going by the datecodes I can see on the caps and on one of the transformers, it looks like they were made around 11-12 years ago or so. So I guess it's not a bad life, despite falling under the 15 year max life spec most manufacturers rate their caps at (but that's if you keep them cool).

Yeah, 12 years isn't too bad and this unit is also not that great either -> Group regulated, 8pin HY-510N without UVP on 12V...