VOGONS


A tale of two PSUs

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First post, by bjt

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When I first put my socket 7 build together I threw out the original 15-year-old AT PSU in favour of this 300W ATX supply:
nkos.th.jpg
Although I didn't realise it at the time, it's pretty bad. Only 60W on the 5V rail, doesn't do -5V, loud fan. Added together all the rails total 315W.

Recently I got hold of this NOS Seasonic PSU from ~2002, also 300W:
0slb.th.jpg
150W on the 5V rail, only 3A less on 12V, does -5V and is very quiet. Added together the rails total 444W. It also weighs nearly twice as much as the Maplin PSU.

How come there's such a massive difference in power output between these two PSUs that both advertise themselves as 300W?

Reply 1 of 472, by TELVM

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About the first one I can tell you with a high degree of confidence that it's a gutless wonder. Probably able of 200~250 real DC watts at the most, if, before fireworks and smoke. This is typical with junkies, they always pretend to offer much more power than what they can really deliver. Here's a notable (for its rare honesty 🤣 ) example from Brazil:

REALPOWER.png
"REAL POWER: 250W" 😵 (as a matter of fact it blew up @ 238W under test 😁 )

With variations due to local folklore, this cheap junk plagues every country of the world.

We shouldn't attach things like that to any comp we value a bit, for even if it takes two or three years to explode it will be flogging the system with murderous levels of ripple from the start. The best we can do is open it, take some pics, post them here so that we can scrutinize how dangerous its guts are, then recycle the crap so that it can do no harm to no comp.

The Seasonic is at the opposite extreme of the scale, a decent PSU that already sported active PFC (still relatively rare at that time) in 2002.

t907994_SS300FS001.jpg t907995_SS300FS002.jpg t907996_SS300FS003.jpg

A classic relic that should be caressed for with fresh fan & caps when necessary. It claims just 300W but will do more without exploding when put to the test. Here's a venerable review at SPCR: http://www.silentpcreview.com/article20-page1.html

bjt wrote:

... It also weighs nearly twice as much as the Maplin PSU ...

Weight is a good giveaway of PSU quality, the heavier the better.

It's not a fail-proof method however, as some junk makers add cement as ballast inside their gutless wonders to deceive us.

Let the air flow!

Reply 2 of 472, by bjt

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Good to know. I've ordered a another Seasonic from the same eBay seller, they're only charging £9 delivered which has got to be a bargain considering the Maplin PSU was twice that.

Reply 3 of 472, by TELVM

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Just make sure you get the active PFC version of the Seasonic SS-300FS (the one in the SPCR article, with a single big cap in the center and 'Active PFC' on label).

The non-PFC version (the one in the small pics above, with two big caps at one side and NO 'Active PFC' on label) ...

t908372_NoAPFC.jpg

... has a two transistor +5VSB circuit, like the notorious Worstecs. Were the original decade-old capacitors in that circuit to fail, +5VSB voltage would rocket skywards, frying the southbridge and killing the mobo. A tinkering vogoner will just recap the PSU and thus render it perfectly OK for another decade or more, but for the not tinkering people there is a potential problem inside nowadays.

In the active PFC version of the SS-300FS the +5VSB is a TOPSwitcher circuit, much safer and solid even if the +5VSB caps go south.

Let the air flow!

Reply 5 of 472, by TELVM

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You took pretty good pics of the internals, congrats! Let's vivisection it.

The juice comes from the wall and first meets the input filtering section, which protects the PSU fron electrical fluctuations and noise coming from the wall, and prevents EMI and RFI (electromagnetic and radiofrequency interference) produced by the PSU from affecting other electronic gadgets in the house.

The worst of the gutless wonders either completely lack any transient filtering or have very little of it, to pinch a penny here and there (like the Brazilian PSU linked above, that has just two Y-caps and nothing more).

This PSU has two common mode chokes (the donuts with copper wire wrapped around), two X-capacitors (yellow boxes), but just one Y-capacitor (light blue lentil with two legs at the corner) when there should be two Y-caps at the least. It has however a ferrite bead in the mains wires, which is a rare touch amongst cheap PSUs:

i908494_MaplinWonder001.png

The rule of thumb for decent input filtering is at least two chokes, two X-caps and two Y-caps. This PSU more or less manages it, and the reason is no other than pressure from current european laws on EMI/RFI.

Next comes the rectifier bridge, which as its name implies rectifies the juice from 230 volts AC to ~325 volts DC. Here they've used four discrete diodes, more penny pinching:

i908496_MaplinWonder002.png

Discrete diodes can't be heatsunk, and laying so low on the ground they catch little breeze, hence they might overheat, derate and blow. A monobloc bridge with heatsink is much better, but cost more pennies.

Note also that the board is silkscreened for a passive PFC coil, which is absent. More cost cutting.

Next come the primary capacitors, which are sometimes called 'the big caps', but not in this case:

i908497_MaplinWonder003.png

Those stumpy caps are marked '470uF' but they are so small that I wouldn't be surprised at all it they were fakes of less real capacitance. More penny pinching. Such undernourished primary caps are bad medicine for ripple handling and power delivery. Being cheapo brand and temp rated at 85C instead of 105C doesn't help either.

As is tradition with cheap PSUs the heatsinks are anoxerically thin (aluminium costs pennies). This is the main reason why junk PSUs are 'flyweight'. Thin heatsinks don't dissipate heat as good as thick ones, so attached transistors and diodes may overheat, derate and blow:

i908505_MaplinWonder004.png

^ The main transformer is decently sized at '35' size.

Finally we reach the output filtering. The caps for the three main rails are small (1000uF all around, the +3.3V and +5V caps should be 2200uF or more) and cheap, unreliable brands (good jap caps cost more pennies):

i908508_MaplinWonder005.png

There is not a single PI coil on sight (copper costs pennies). The +12V rail is particularly bad here, it should have a filtering ouput with two caps flanking one PI inductor:

i908507_PIFilter001.jpg

Instead there is no PI coil and only one single, small cap on this rail. That guarantees that +12V ripple will be beyond the roof and out of ATX spec. This murders HDDs, amongst other nasty effects.

Now if you don't mind we need the last pieces of info to complete the vivisection 😁 . Keep up the great work and please read and post here what is written on the three transistors attached to the primary heatsink, and also on the three rectifier diodes attached to the secondary heatsink. They are all like small black boxes with three metal legs, here is an example from another PSU:

i908509_PrimarySwitchers001.png

i908510_SecondaryRectifiers001.png

With this info we will know what power this PSU can really deliver on each rail and overall.

Let the air flow!

Reply 7 of 472, by keropi

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jwt27 wrote:

Pretty amazing how you can pull all that information from just a few pictures, hats off! 😳

indeed! kudos!
it made me to disassemble my main p1 build and take these pics:

th_20131225_231348_zpsa88d58ff.jpg th_20131225_231056_zpsdcc69b20.jpg th_20131225_231135_zpsec23c0b0.jpg th_20131225_231148_zpsfc3359e9.jpg

th_20131225_231115_zps6f70267e.jpg th_20131225_231105_zps3f74be0a.jpg th_20131225_231041_zps97166c22.jpg

so what's the verdict TELVM ? was it a good purchase for a p1 machine? 😕

🎵 🎧 PCMIDI MPU , Orpheus , Action Rewind , Megacard , MK8330 and 🎶GoldLib soundcard website

Reply 9 of 472, by TELVM

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@ Keropi - Chieftec GPA-450SB

· Euro PSU: Brown/blue mains wires (americans are black/white).

· Very good input filtering: 2.5 chokes (the little yellow one is only on line/hot), 2 X-caps, 4 Y-caps, and even a MOV (between yellow choke and X-cap, ZNR1 mark on the board, the yellow lentil wrapped in black heat shrink) to protect from surges.

· Decent monobloc bridge rectifier (as opposed to the four diode treatment). It's the black flat thing standing upright on four metal legs and marked 'GBU606'. The first '6' is the ampere rating, 6 Amperes. 230V x 6A = 1380 Watts it can manage, theoretically. The second '6' means it can handle 600V of reverse voltage. They didn't attach a heatsink to this bridge rectifier (penny pinching on aluminium), which is bad practice as it derates it to half the watts, but shouldn't matter for a 450W PSU.

· Active PFC. At 220uF the single big cap is a bit on the edge of decent size for a 450W PSU, 270 or 330uF would be better (400 volt caps are expensive and they often penny pinch on them). Can't see the brand.

· The main transformer looks beefy enough.

· Unfortunately come to this point what was being a decent PSU goes down in flames: I notice caps of the dreaded 'Jun Fu' brand onboard 😵 😵 😵 😵 😵 . These are about the worst caps in the world, very unreliable.

800px-Bad_cap_PS.png <== CRAP!!!

Penny pinching at its worst. Some of them are on the +5VSB circuit ... gulp ...

· Output filtering: As far as the wire bundle allows to see, there seems to be two caps and one PI coil for each main rail, which is good. The caps seem to be 1000uF, they should be beefier. Can't really read their brand but from a distance look cheap.

Overall decent hardware, ruined by the ridiculous inclusion of the Jun Fu crapacitors. With good jap caps of beefier sizes this PSU would be quite decent.

You don't need 450W to power a less than 100W retro system, it would have been much better to invest the money on a PSU with less watts but better caps (those Jun Fus are a crime 😵 ).

@ bjt - Maplin Wonder

You're a great macro photographer of PSUs! Congrats! 😎

The 2N65 is the +5VSB transistor. As befitting this gutless wonder it is rated as just 2 Amperes (you plug several USB gadgets, that draw from +5VSB, and it blows up), and has an obscene RDS(on) of 3.9~5 ohms which makes for a very high standby power draw .

The two 13007 switching transistors are rated at 8A and tipycally explode at about ~250W (see brazilian wonder above also with 13007s blowing up @ 238W).

The +3.3V rectifier is a 20C45 Schottky, rated at 20A max => 3.3V x 20A = 66W tops on the +3.3V rail.

The +12V rectifier looks like a chinese copy of a 1620 ultrafast. Ultrafasts are less efficient than Schottky diodes (more penny pinching). It's rated at 16A => 12V x 16A = 192W tops on the +12V rail.

The +5V rectifier is a 20C45 like the +3.3V one. 5V x 20A = 100W tops on the +5V rail.

66 + 192 + 100 = ~350W theoretically. Unfortunately the 13007 switchers will explode about ~100W below that.

EDIT - By the way, just for the scientific interest, the Maplin's label pretends to have two +12V rails ('+12V1' and '+12V2'). That's just a lie, there's only one +12V rail.

Let the air flow!

Reply 10 of 472, by RacoonRider

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TELVM, since you're obviously quite experienced in PSUs, do you think a Powerman 450W rated PSU can be the reason for 3 PCI-E videocards failing one after another in the same PC? I'm starting to think I need a replacement.

Reply 11 of 472, by keropi

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@TELVM

thanks for the analysis!!! I might go ahead and replace the JunFu caps when I come around and order some decent ones... unfortunately all I can find locally are LELON caps and nothing else... :\
I know that the psu is an overkill for a p1 but you can't really get a smaller one now days... reason I got this was because it had active PFC and 80+ so I thought it would be good enough for a p1...

I have a small favor to ask, when and if you have the time, can you look HERE and recommend me a psu that costs around 50e for the p1 build? you can select makers from the top list and the bottom list will be filtered... I have no idea how to look for a good psu... 🤣

🎵 🎧 PCMIDI MPU , Orpheus , Action Rewind , Megacard , MK8330 and 🎶GoldLib soundcard website

Reply 12 of 472, by Forevermore

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This thread needs to be stickied.

That's a lot of vital information there for the less knowledgeable TELVM.

So many combinations to make, so few cases to put them in.

Reply 13 of 472, by TELVM

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RacoonRider wrote:

TELVM, since you're obviously quite experienced in PSUs ...

🤣 far from it, I'm just a hobbyist that loves tinkering. Not so long ago I was afraid of opening PSUs 😁 .

RacoonRider wrote:

... do you think a Powerman 450W rated PSU can be the reason for 3 PCI-E videocards failing one after another in the same PC? I'm starting to think I need a replacement.

Might be, but I'd look first if the mobo is OK.

Keropi wrote:

I might go ahead and replace the JunFu caps when I come around and order some decent ones...

That's what I'd do, that Chieftec looks otherwise decent. With real caps it would be OK.

Keropi wrote:

... unfortunately all I can find locally are LELON caps and nothing else...

Lelons are also crap, barely better than Jun Fus. If we recap better to do with top notch japanese caps, these are The Four Magnificents: Nichicon, Panasonic, Rubycon, United Chemi-Con.

I usually buy caps from Farnell, look at 'All products > Passive components > Capacitors > Aluminium Electrolytic Capacitors - Leaded' (for smaller caps) and at 'Aluminium Electrolytic Capacitors - Snap In' (for big caps).

Digikey is another source.

If you go ahead with the recap I can lend a hand selecting the new caps, make a list with all the caps in the PSU noting brand, uF, V, diameter and position.

Keropi wrote:

... I know that the psu is an overkill for a p1 but you can't really get a smaller one now days ...

There are plenty of decent 300~350W PSUs nowadays.

Keropi wrote:

... reason I got this was because it had active PFC and 80+ so I thought it would be good enough for a p1 ...

We don't need neither PFC nor high efficiency to power our venerable relics. PFC only benefits the electrical company, it's indifferent to us users (except for raising PSU cost that falls upon us).

Efficiency ('80+ gold/platinum/unobtainium') matters a lot with a 1200W system folding 24/7/365, but with a 75W Pentium III (that we only switch on ocasionally to play Half-Life for a couple hours) efficiency is really irrelevant.

Keropi wrote:

... can you look HERE and recommend me a psu that costs around 50e for the p1 build? ...

· 37.90€ COOLERMASTER RS400-PSAPI3-EU ELITE POWER 400W - Review of Euro version with passive PFC and Review of american version without PFC. Should do decently for low-power retrocomps. Taiwanese Teapo caps are mediocre, not as good by any chance as jap caps, but better than Jun Fu ticking bombs. However for the same price you can get the following:

· 37.93€ BE QUIET! SYSTEM POWER 7 300W - German Review. I like this little one, looks quite decent. Teapo caps.

· 44.90€ Corsair CX430 - Review, review and review. More than is needed for any retrocomp. Teapo and Samxon caps (Samxons are better than Teapos).

*** Stay away from this one, it's just another example of potentially decent PSU ruined by including the dreaded Jun Fus: http://translate.google.com/translate?hl=es&i … y/36_32736.html

Let the air flow!

Reply 14 of 472, by keropi

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Awesome info, thanks for the replies TELVM!
The only reason I don't order from farnell/digikey is that they charge shipping to Greece, IIRC it was something ~30eur , unless you make a 65+eur order in which case it is free.... I could just get another psu for that money... 🤣
Do you think that under a p1's load the JunFu caps are dangerous?

🎵 🎧 PCMIDI MPU , Orpheus , Action Rewind , Megacard , MK8330 and 🎶GoldLib soundcard website

Reply 15 of 472, by RacoonRider

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I think all this stuff is worth adding to vogonswiki 😀

TELVM wrote:

Might be, but I'd look first if the mobo is OK.

Asus P5B, no bad caps or anything... I'll open up the PSU this weekend)

Reply 16 of 472, by TELVM

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keropi wrote:

The only reason I don't order from farnell/digikey is that they charge shipping to Greece, IIRC it was something ~30eur , unless you make a 65+eur order in which case it is free....

Ouch, that's a problem 🙁 .

Just in case you'd think about it: Beware of caps selling on ebay, many are fakes (you think you are buying a Rubycon and it's really a Jun Fu in disguise 😵 ).

keropi wrote:

... Do you think that under a p1's load the JunFu caps are dangerous?

Jun Fus are ticking bombs, I wouldn't wish them to my worst enemy. That said, a very low power draw P1 system only switched on ocassionally should stress them minimally, maximizing longevity (whatever it would be 🙄 ).

Overkill cooling would also help, heat murders all lytics but crap caps pop like corn under heat. If the PSU fan is the only exhaust one in the system, you can add extra case exhaust fans to 'unload' heat from the PSU, and/or flip the PSU fan so that it pulls fresh air from the exterior 😉 . Every bit helps.

RacoonRider wrote:

... I'll open up the PSU this weekend ...

Good, more vivisection 😁 .

Just remenber: SAFETY FIRST!

Never NEVER EVER fiddle inside a PSU that is still plugged to the wall!!! 😳 😳 😳 😳 😳

A 230V PSU plugged to the wall can administer you 325 volts, that can and will kill you!!! 😵 No Darwin awards please!!!

Don't trust the rear PSU switch, always unplug from wall!

Once unplugged from the wall, the internal bleed resistors render the PSU safe in a matter of seconds.

But for extra paranoid safety, better wait for some minutes after unplugging before opening the PSU, just in case 😀 .

Let the air flow!

Reply 17 of 472, by keropi

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@TELVM

I'm sold... need to replace the caps asap... or get another one in the meantime (the COOLERMASTER RS400 is in stock atm, the 2 others take ~10days)

Now, I took some more photos 🤣 🤣 🤣 😊 , it's an older ATX psu that is surprisingly heavy and quiet despite it's 2 fans... it also has -5v and although it works it needs at least 5 caps replacing (all tall ones near the output cables and a smaller 470uF one next to the purple cable), but how is it's overall quality? does it worth the time to buy and replace caps or no?

th_Cimg1857_zpsdc282732.jpg th_Cimg1855_zps132432d5.jpg th_Cimg1856_zpsbbdfce6f.jpg th_Cimg1858_zps53b2f459.jpg

th_Cimg1867_zpsb6dbfa3b.jpg th_Cimg1860_zps3805b410.jpg th_Cimg1866_zps8efc3ff1.jpg th_Cimg1865_zps5a33e479.jpg

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as always, input is highly appreciated 😊

🎵 🎧 PCMIDI MPU , Orpheus , Action Rewind , Megacard , MK8330 and 🎶GoldLib soundcard website

Reply 19 of 472, by TELVM

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keropi wrote:
http://i125.photobucket.com/albums/p55/restqp/temp/th_Cimg1864_zpsba826152.jpg […]
Show full quote

th_Cimg1864_zpsba826152.jpg

^ That's what happens with crap capacitors, in this case the infamous Fuhjyyus (aka 'Fuckyous'), that rival the Jun Fus in (lack of) quality. Don't power any comp you value a bit with this PSU while defective caps are onboard.

This is an old style half-bridge '+5V heavy' PSU with 30 x 5 = 150W on the +5V rail. Passable input filtering, well sized transformer and thick heatsinks. It seems to lack the small toroid ('donut' coil) in the output filtering for +3.3V, perhaps there is a regulator for +3.3V somewhere.

Output-filter.jpg
^ Pic from C_hegge's Hardware Insights

There are PI coils on at least two rails (you should move aside the wire bundle before taking pics, occludes much of the output filtering 😀 ).

Good material for recapping practice, all those Fuckyous and Crapxons need to be kicked away and replaced with real caps.

Let the air flow!