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perkyzombie

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    perkyzombie got a reaction from Spotty in My PC made a very loud buzzing sound and then emedieatly shut down and wont turn back on   
    I recently purchased Kentek because curiosity, mine is rated at 550w however the rating which interested me is the 5 volt rail at 40 amps. This is relative for P3, P4, Athlon XP systems. The 3.3v and 12v rails are only rated to 25amps, which is likely low on the 12v for modern gaming systems. Indeed a quick look at the rail specifications for the Kentek 680w, this is truly meant for the last of the 32bit systems, see picture, only 22amps on the 12v... that's why it blew on a modern system.
     
    After opening the 550w unit it is clearly a knock-off, I suspect the PCB is copied for an Enermax or SH circa 2002ish. However, all the AC interference suppression components were not populated and only the minimum of the electrolytic caps are populated. The PSU is a basic full-bridge rectifier with near no power conditioning.
     
    Admittedly, I'm quite the Corsair fan boy as I've six systems using their PSUs, 5 of which are the HXi series. I've not bothered or had the need to crack any of the HXis open and my only gripe regarding things Corsair is the complete lack of linux support but that's just typical and irritating.
     
    However(!), the sixth PSU is an older TX750W which had two issues. The axial fuse on the AC supply had a cold solder joint on an axial lead which eventually failed. This cause intermittent operation and the typical zzt sound as the connection went in and out of contact; easy fix.
     
    While I was poking around the PSU looking for the failure I desolder the AC film capacitor which is used for interference suppression. Not impressed here, these are the cheapest of the cheap, China X2s. Likely, the PSU experienced an overvoltage event which can really wreak havoc on film caps; mine was operating at 60% capacitance. I'm a huge fan of the Panasonic film caps as they have a fused grid array which limits breakdown propagation. I use these on all PSUs I refurbish (as well Nichicon PM or PW series electrolytic caps for PSU and motherboard power cap replacements -good high ripple current and ~0 ESR)
    https://industrial.panasonic.com/ww/products-cap/film-capacitors/film-cap-electroequip/radial-features
     
    The better the interference suppression the less the AC leakage into the DC supply and the less ripple current the motherboard caps have to deal with as well swtiching transients. Modern motherboards which are somewhat decent have all made the switch to polymer caps in lieu of electrolytic caps, polymer caps have ripple suppression ratings typically five or more times higher than the equivalent sized electrolytic as such they are far more tolerant to crapy PSUs... they are also 5 times the cost.
    https://www.tomshardware.co.uk/power-supplies-101,review-33299-3.html
     

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