the gutless, bloated, and fried power supply hall of shame

[momaka]

Re: the gutless, bloated, and fried power supply hall of shame

^ I did that with a JNC PSU many years ago. It was as gutless as a PSU could get from the early 2000's, but still had a ton of useful components. As such, I'm still using parts from that thing, even to this day. It's mostly the resistors, but other more specific components too, occasionally. One would think those small resistors aren't that useful or special. But when repairing something and you need a specific value, they actually come in very handy. This is the PCB after I finished stripping it:


And here is the entire post:
https://www.badcaps.net/forum/showpo...&postcount=165
Fun fact: I still keep that PCB around - I'm re-using the big solder blobs from it.
Well, that, and in case I need to figure out the transformer output windings configuration (in case I may need to re-use it.)

Actually, just a few days ago I re-used the crappy output toroid inductor from that PSU to test-fix an old BFG "550 Watt" PSU. Using the PCB as a reference, I was able to determine the windings on the output toroid from the JNC PSU and use it on the BFG, because the BFG was all burned up. Here is the post about it:
https://www.badcaps.net/forum/showpo...36&postcount=2

[Dannyx]

Re: the gutless, bloated, and fried power supply hall of shame

It might not even have many parts worth salvaging.

Actually, it did: I stripped the entire board, I mean ALL OF IT: resistors and everything You have no idea how much I'm starving for parts over here

[PeteS in CA]

Re: the gutless, bloated, and fried power supply hall of shame

I'm going to concur with momaka, the big lytics probably failed when one of the rectifiers in the bridge shorted and the caps saw reverse voltage. While the label value of 470uF in that configuration would probably be OK for 250W, that inverter heatsink puts the useful power (if operating) at around 200W. And if the rest of the PSU is as skimpy as the non-existent power line filtering, that might be pushing it. It might not even have many parts worth salvaging.

[Dannyx]

Re: the gutless, bloated, and fried power supply hall of shame

Also, for half-bridge PSUs, you must have two series caps on the input. That way, the input voltage is divided equally. The "center tap" or "middle connection" of these series caps goes to one side of the main PS transformer on the primary (through a metal film cap). The other leg on the primary side of the main PS transformer is switched between +340V and primary GRND by the two BJTs. So this creates a series of square wave pulses with 170V amplitude across the main PS primary side. On the secondary side, you have center-tapped windings for a 5V rail and 12V rail, from which the 3.3V, 5V, 12V, -5V, and -12V rails can be derived.

Thanks for this...to this day I must admit I'm not all that knowledgeable about the operation of SMPSs, esp. ATX ones - I know the basics enough to fix them (when worth it), but don't know their operation in great detail. For instance, until quite late in my electronics career, I had no idea what the third small transformer is for in most units - I now know it's for feedback (though still not sure for which rail). I always thought it was for the 3.3v output...

[momaka]

Re: the gutless, bloated, and fried power supply hall of shame

Oh man, that ^... is soo gutless!

Even if the PSU didn't have any damage, I would NOT use it for anything - not even powering small DC fans.

Severely failed mains caps on a trash-picked RPC ATX supply.
...
Two diodes of the bridge were shorted.
...
The fan was not seized when I found it (so I kept it ), so the cause of failure wasn't actually excess heat, but likely overvoltage !

Looks like it.
I don't see an input voltage selector switch, so it's not possible for someone to have set the PSU for 115V AC operation and then plug it into 230V AC (which is one way to cause this kind of damage to the primary caps.)

Instead, it looks like either one or more of the diodes in the full "bridge rectifier" on the input overheated and shorted, sending AC current to the input caps...
-OR-
There was a power surge from nearby lightning strike hitting a power line and causing massive over-voltage.

I imagine this PSU came from the city, where majority of AC power distribution to residential buildings is underground. So that means caps likely blew because the diodes in the bridge rectifier failed.

Look at those caps more carefully: only 200v rating ? There's no PFC here, so although B+ doesn't go as high as 400v, I know for a fact it's still around 300+ after the bridge rectifier, making a 200v rated cap about 100v too low ! Could it be they're in series ?

Yes, the two primary caps in these cheapo PSUs without APFC are -ALWAYS- in series. So the total DC voltage they can handle is 400V, and total capacitance is half, or approx. 235 uF, assuming they are real capacity 470 uF caps (given the dubious cap brand, that is an optimistic assumption. )

Also, for half-bridge PSUs, you must have two series caps on the input. That way, the input voltage is divided equally. The "center tap" or "middle connection" of these series caps goes to one side of the main PS transformer on the primary (through a metal film cap). The other leg on the primary side of the main PS transformer is switched between +340V and primary GRND by the two BJTs. So this creates a series of square wave pulses with 170V amplitude across the main PS primary side. On the secondary side, you have center-tapped windings for a 5V rail and 12V rail, from which the 3.3V, 5V, 12V, -5V, and -12V rails can be derived.

Also, have a look at that top "shelf" of the heatsink. Yes, that's right: the force of the can being "ejected" upwards was so great that it bent the corner of the heatsink. I myself wouldn't be able to do that bare-handed

Yeah, when caps explode fast like that, they can cause quite a bit of damage.
I have an old L&C/Deer PSU, whose unfiltered high-side 5VSB cap exploded and also bent a fin on the secondary-side heatsink, just like on your unit.
Give me a few minutes, and I'll edit this post with a link to that PSU (I posted it on BCN many many years ago.)

**EDIT**
Here is the PSU/picture in question:
https://www.badcaps.net/forum/attach...2&d=1331835289
Notice the two "ears" sticking out on a component? (Just a little left from the center of the image.) Those are the leads and rubber bung left from that exploded cap. The cap can probably hit the heatsink fin right above it and bent it. I couldn't find the cap can body anywhere, though. It must have fallen out when I found that PSU (it was a trash can find many years before I was even into fixing electronics.) There was simply paper and aluminum shrapnel/shards/pieces everywhere inside the PSU. This is why I always wear safety glasses when testing PSUs with covers removed or when testing a circuit on my breadboard that involves small caps and the possibility of them getting either over-volted or reverse-voltage (though I usually design to try to avoid that, of course.)

Here is the post I made about it, from 8 years ago, mind you (wow I feel old now! )
https://www.badcaps.net/forum/showpo...&postcount=489

[Dannyx]

Re: the gutless, bloated, and fried power supply hall of shame

Severely failed mains caps on a trash-picked RPC ATX supply. I dug this out of our junk pile the other day with intent of scavenging for parts, when I saw THIS The vent on the cap on the left apparently failed to open up, forcing the pressure to release out the bottom. Fuse was completely blown to bits (visible to the right). Two diodes of the bridge were shorted. BJTs were OK, so likely fixable overall, but what's the point when the caps cost almost as much as the whole thing when new ?

Also, have a look at that top "shelf" of the heatsink. Yes, that's right: the force of the can being "ejected" upwards was so great that it bent the corner of the heatsink. I myself wouldn't be able to do that bare-handed

The fan was not seized when I found it (so I kept it ), so the cause of failure wasn't actually excess heat, but likely overvoltage ! Look at those caps more carefully: only 200v rating ? There's no PFC here, so although B+ doesn't go as high as 400v, I know for a fact it's still around 300+ after the bridge rectifier, making a 200v rated cap about 100v too low ! Could it be they're in series ?.....but that would also drop capacitance ! I tossed the board now, so I forgot to check, for curiosity's sake. TBH, I didn't even notice that 200v marking until just now when I was transferring the photos off my phone to upload them Am I mad ? 200v caps on the hot side of a SMPS ? Is it intended for a 110v country ? Maybe they were in series after all....:|

[Dan81]

Re: the gutless, bloated, and fried power supply hall of shame

It looks like its Y-caps are safety rated types, though.

They're not.

I've had 2 Delux PSU with the same PCB and the caps read "472 1KV" on both.

[PeteS in CA]

Re: the gutless, bloated, and fried power supply hall of shame

Yeah, that Lametech looks like it could be a usable 200W P/S - limited by the 330uF F-yus, where's-the-beef heatsinks, under-sized main transformer, wimpy output rectifiers, almost-tiny toroids and AWG #20 output wires. It looks like its Y-caps are safety rated types, though.

[Dan81]

Re: the gutless, bloated, and fried power supply hall of shame

Yeah, that's the same platform used in MOST Delux units. Pretty moddable if you ask me. I've actually improved one of these for a quite low power i3 unit w/ GTX1050 (w/o PCI-E plug, MSI branded) and it's been holding up great.

Ironically HKC PSUs did a better attempt at this, and if it weren't for the quite skinny heatsinks in mine, it might actually do 430W.

[momaka]

Re: the gutless, bloated, and fried power supply hall of shame

Lamtech ATX-S450

Personally, I find this psu boring.

While most of the components are there, they are just too small.

Agreed.
Looks like a decent *try*, but just a tad bit short of being overall decent PSU.
15A on the 12V rail will do for a basic system, if it can provide that much in spec. With 2 output caps and a PI coil, it probably will - just barely, if the caps on the 12V rail are 1000 uF each (and they look like they are.) Still, it ticks me off to see a 450 Watt rating on the label. If they advertised this as a basic 200-250W PSU and sold it for the right price, this would be much better alternative than, say... Powertech or L&C.

The primary caps are 330uF, too small to take this unit seriously and who knows if this is their real capacitance.

Fuhjyyu MK, I see. Generally speaking, Fuhjyyu... no matter how crappy people say they are... don't lie about their capacity. I personally would take them any day over CapXon.

More like LAMEtech

LOL
Still better than L&C (Lame and Crappy )

[TechGeek]

Re: the gutless, bloated, and fried power supply hall of shame

More like LAMEtech

[goodpsusearch]

Re: the gutless, bloated, and fried power supply hall of shame

Lamtech ATX-S450

Personally, I find this psu boring.

While most of the components are there, they are just too small.

The input filter is here, missing a common mode choke and MOV.

The conductive glue is here too. Good!

The 4 diodes are tiny but probably good for 230V AC.

The primary caps are 330uF, too small to take this unit seriously and who knows if this is their real capacitance.

half bridge design with switching transistors 2x D13007

very small transformers 33 and 16

nicon caps everywhere

pi coil for every output voltage and 2 caps for all voltage rails except -12V

tl494 and SDC339 ICs

very small toroid coils

S16C45C @ 3.3V
S20C45C @ 5V
F16C20C @ 12V

This unit was made in 2011 and looking at the label:
15A @ 12V
there is no excuse for that

The label also states that there is -5V rail and the white cable is there, but the place for -5V output cap is not populated on PCB.

[momaka]

Re: the gutless, bloated, and fried power supply hall of shame

Beware! The most powerful Powertech power supply ever posted here!

Powertech ATX-550W

Well, compared to the other Powertech PSUs, it indeed has really good build quality. (Not that they were setting the bar too high to begin with. )

label states dual 12V rail and 17A on each one with no max combined output limit!

*Sigh*
If only they gave it an honest 250W rating with maybe a limit of 200W on the 12V rail, that PSU wouldn't actually been half bad.

The fan brand is "Cooling fan". Cool

What a creative fan name

There is also a full input filter, except the MOVs because they are expensive!

Who needs those stinkin' MOVs?! don't you know they blow up when there is a surge and then the fuse blows and PSU stops working. Isn't it much more interesting when the primary caps blow instead?

This unit broke the chinese tradition and even has an IC controlled 5vsb :
em311Z

I searched but couldn't find a datasheet.

I'm guessing that would be FSDM311 clone??
https://cdn.badcaps-static.com/pdfs/...0ea56a5952.pdf
Check if the pinout matches.
Probably does. I don't see what else it would be.
Not bad. Everell here did a mod like that to convert many Bestec ATX-250-12E power supplies, and it works pretty well. Will handle up to 2-2.5 Amps

and the rectifier for 12V is mur2020ct, rated for 20A.

Wow. An actual Schottky rectifier for the 12V rail. Shocking!

And there is a fan controller with thermistor ghetto glued on secondary heatsink

OK, this must be the golden engineering sample or something.

[goodpsusearch]

Re: the gutless, bloated, and fried power supply hall of shame

Beware! The most powerful Powertech power supply ever posted here!

Powertech ATX-550W

label states dual 12V rail and 17A on each one with no max combined output limit!

The fan brand is "Cooling fan". Cool

There is also a full input filter, except the MOVs because they are expensive!

How is the 5VSB on these units, is it "two transistors" design or something decent?

This unit broke the chinese tradition and even has an IC controlled 5vsb :
em311Z

I searched but couldn't find a datasheet.

half bridge psu with 2x 13007 again

the rectifiers for 3.3V and 5V are MBR2545CT

and the rectifier for 12V is mur2020ct, rated for 20A.

So, it is indeed really powerful compared to the other Powertech units.

And there is a fan controller with thermistor ghetto glued on secondary heatsink

[momaka]

Re: the gutless, bloated, and fried power supply hall of shame

The TO247 12V rectifier also did not fit since the board only allows TO220 parts there, so i had to bend the legs of the rectifier and make a new mounting hole on the heatsink to mount it higher in order to make it all fit.

That's funny.
With other gutless PSU's I've seen (particularly ones that were based on a "high end model" PCB and then made cheaper), they would have TO-247 holes, but only TO-220 parts installed, with the TO-220 parts' pins stretched to fit the holes, lol.

Powertech ATX-450W year 2014
...
Something bad happened here as you can see from the toasty group of resistors.

Bad caps on the 5VSB caused the 5VSB to go out of regulation and probably over-voltage on its secondary-side auxiliary rail, possibly killing the PWM controller as well. I've seen it enough times now that I don't skip recapping the 5VSB of a PSU if I care about using it long term.

why? I mean, this is not an early 00s unit. It's a 2014 psu. Why put 20A and 30A on 3.3V and 5V rails and 12A ultrafast rectifier on 12V?

Old Chinese traditions.

I don't think the manufacturer cares much considering this unit would require PFC to be sold in the EU though, yet there is none.
And since it is rated for 230VAC input only I guess they had no plans to sell it anywhere else...

Well, there are a lot of places besides Europe that also use 220-240V mains, yet don't require PFC (even China has a big internal market, I suppose.)

But yeah... not like the manufacturer seems to care anyways.

How is the 5VSB on these units, is it "two transistors" design or something decent?

Of course! Was there ever any doubt?
Like I said... old Chinese traditions must be observed.

[Per Hansson]

Re: the gutless, bloated, and fried power supply hall of shame

Well the label on the powewr (sic) supply is what informed people base their purchasing decisions on.
And that assures of a hefty 29A on 12v, and then just 10A on 5v and 14A on 3.3v.
Sounds like a quite modern unit don't you think?
I mean we have come a long way comparing it to the label on this don't you think?
It is almost like they have listened to your initial feedback there and then made some serious iterations.
In this latest one is the PFC connector spot maybe even upgraded so it sits between live a neutral and not just off to the side not connected to anything?

I don't think the manufacturer cares much considering this unit would require PFC to be sold in the EU though, yet there is none.
And since it is rated for 230VAC input only I guess they had no plans to sell it anywhere else...
How is the 5VSB on these units, is it "two transistors" design or something decent?

[goodpsusearch]

Re: the gutless, bloated, and fried power supply hall of shame

Powertech ATX-450W year 2014

I have also the 2012, 2013 and 2015 versions of this thing.

No one is even close to half decent.

Something bad happened here as you can see from the toasty group of resistors.

2x 13007 npn transistors

EST7502C supervisor IC

MBR2545CT 3.3V

MBR2060CT 5V

F12C20C 12V

why? I mean, this is not an early 00s unit. It's a 2014 psu. Why put 20A and 30A on 3.3V and 5V rails and 12A ultrafast rectifier on 12V?

[bauto601]

Re: the gutless, bloated, and fried power supply hall of shame

This looks like an Athena Power unit, definitely better than the one i pulled about 2 years ago as yours seems to have more room for modifications.

I have 3 of these units and the internals are exactly the same. The 2 other units have got a different label that include an UL number that points to Sun Pro / Raidmax i believe. I have readen somewhere on this forum that a grey/metal colored fan label also is a pointer to Sun Pro/Raidmax, as is the case on all 3 units i have here. The PCB itself does not have any clear serial numbers that point towards a certain manufacturer unfortunately.

And talking about room for modifications... The second cap for the 12V rail is added at the place where you normally put the outgoing wires. The PFC connector is not mounted directly to the PCB as they never even bothered to add PFC support on it. The bigger output inductor did not really fit and i had to use some additional solid core wiring and modify the secondary heatsink to make it fit, the ERL35 transformer had the same footprint as the ERL33 transformer and even that one i had to squeeze in and change the primary heatsink for. The TO247 12V rectifier also did not fit since the board only allows TO220 parts there, so i had to bend the legs of the rectifier and make a new mounting hole on the heatsink to mount it higher in order to make it all fit. The fan control circuit is also added via an additional PCB, at least the bridge rectifier popped right in.....

[RukyCon]

Re: the gutless, bloated, and fried power supply hall of shame

This looks like an Athena Power unit, definitely better than the one i pulled about 2 years ago as yours seems to have more room for modifications.

[bauto601]

Re: the gutless, bloated, and fried power supply hall of shame

hmmm.
If it was my unit, i would have put that 2200 uf cap on the 5vsb rail. 5vsb caps see far more stress than any other rail, since it is always on and filters a flyback design (higher ripple current output.)
the -12v rail no one cares about. Just has to be there and not too out of spec to trip uv/ov protections. Same goes for the -5v rail.

I will change those caps too as soon as the electronics store here opens again, they provide genuine Pannies. (in 2 weeks time or so) Unfortunately i only had the 3 panasonic caps laying here, all the other swapped caps come from used units. Since this unit got a 2012 date code and was unused, i took the gamble that the 5vsb caps will hold up for now. The 2200uf teapo / 1000uf chengx caps didn't fit in the 5vsb spot unfortunately.

another option you can do if you want to keep the -5v rail (for legacy purposes) is to install a 7905 voltage regulator and use the -12v rail to generate -5v with the 7905 regulator. Plus, it's easy - just mount the 7905 on the secondary heatsink and run wires from -12v, -5v, and grnd to the appropriate pins.

It can be done. But to be honest, this psu is going to be used in a modern system, and -5v was only really needed for isa and old pci cards. Oh, and the ocz rambooster also liked to have a -5v rail. Because the psu already is quite compactly packed, adding components that won't be used does not make that much sense. If i was going to use it for older hardware i would certainly add the circuitly for better compatibility.

those are not bad results at all. Pulling 220 watts from the 12v rail is actually impressive given how compact this unit is. Not surprised at all with the temperatures. Now put it in a core 2 duo box that uses no more than 100 watts, and this psu will probably have a very long life and run much cooler.

I was quite impressed by the stability of the power supply. During the load test it ran a little on the hot side, but not too hot. Inductors, transformers and way overspecced rectifiers usually run perfectly fine at these higher temperatures. It probably classifies as a good 250w unit with 12v heavy systems or as a 300w unit when the 5v rail is also loaded a bit more heavily.

The pcb traces are fairily short because of the small pcb, filling the main power traces on the secondary side with solder tin also helped a bit i think. This helps the voltage regulation too.