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

[Viperel]

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

It's +5V heavy, you should load the rail as well. At least couple amps.

Well the same 80W bulb takes the 5V line down to 4.8v which is actually in the +/- 5% specs but i would not trust it hooked to a PC.

[momaka]

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

Well the same 80W bulb takes the 5V line down to 4.8v which is actually in the +/- 5% specs but i would not trust it hooked to a PC.

Ay, that PSU is no good then - not for powering a computer anyways. Maybe okay for playing with LEDs or small motors that don't care about smooth voltage. After all, those caps on the output are indeed too small, as Dan81 pointed out.

Good only for smashing.

Well, not exactly. There are still good parts in that power supply. They are just not good enough to make a functional PC PSU. But if you take the "crappy" schottky rectifiers from this PSU and put them in say, a small 10-20 Watt power adapter that uses regular diodes for the rectification, you would get a lot less heat and much better efficiency. Or, if you're game, you can build your own custom SMPS for something like an amplifier, like our other fellow Romanian, Th3_uN1Qu3, did many ages ago :

https://www.badcaps.net/forum/showthread.php?t=10491

From the looks of those pictures, looks like the black Line wire is going to Neutral and the white neutral wire is going to Line. Be careful with that one and don't get electrocuted - or start a fire!

It actually doesn't matter that much where he lives. Many countries in Europe use the type-F Schuko plug. And with those, Live-Neutral polarity is ambiguous (i.e. L/N can be swapped, depending on which way you insert the plug).

https://en.wikipedia.org/wiki/Schuko

As long as you are aware of that (especially if working on live stuff), it's not too much of a problem. And of course, if designing something with a line switch, you should always use a double-pole switch so that both Live and Neutral are disconnected.

[TechGeek]

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

ay, that psu is no good then - not for powering a computer anyways. Maybe okay for playing with leds or small motors that don't care about smooth voltage. After all, those caps on the output are indeed too small, as dan81 pointed out.


Well, not exactly. There are still good parts in that power supply. They are just not good enough to make a functional pc psu. But if you take the "crappy" schottky rectifiers from this psu and put them in say, a small 10-20 watt power adapter that uses regular diodes for the rectification, you would get a lot less heat and much better efficiency. Or, if you're game, you can build your own custom smps for something like an amplifier, like our other fellow romanian, th3_un1qu3, did many ages ago :

https://www.badcaps.net/forum/showthread.php?t=10491

it actually doesn't matter that much where he lives. Many countries in europe use the type-f schuko plug. And with those, live-neutral polarity is ambiguous (i.e. L/n can be swapped, depending on which way you insert the plug).

https://en.wikipedia.org/wiki/schuko

as long as you are aware of that (especially if working on live stuff), it's not too much of a problem. And of course, if designing something with a line switch, you should always use a double-pole switch so that both live and neutral are disconnected.

+10

[Behemot]

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

Well the point is to load both rails *at the same time*. Loading only one at a time is called crossload and group-designs don't like that. Group regulated units are even worse.

[PeteS in CA]

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

Actually,that might be another 0W PSU,as there are absolutely no PI coils (or ANY SPACE printed on the PCB for them,let alone holes),thus it won't do a watt in spec. Good only for smashing.

Speaking more seriously, I've worked in power electronics for over 35 years. Those semiconductors, heatsinks, and magnetics are probably good for 200W continuous. The output noise would probably have horrible noise spikes (due to the lack of what you called "Pi coils"), and the conducted noise would probably be horrible, due to the lack of input inductors.

But if loaded to 450W, its life would be minutes or even seconds. Those input rectifiers are probably not good for that much current; the MJE13007-clone transistors are not good for that much current (and their beta would probably be less than 5!); the heatsinks aren't adequate for that much heat dissipation, the transformer core might saturate, and the output rectifiers probably aren't good for that much current.

[TechGeek]

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

Transformer core might saturate?????

[momaka]

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

Transformer core might saturate?????

https://en.wikipedia.org/wiki/Saturation_(magnetic)

Basically, each time one of the transistors on the primary switches ON and OFF, you get a pulse of current. This pulse of current travels through windings on the primary side of the transformer and creates a magnetic field inside the metal "walls" of the transformer (i.e. the core). The windings on the secondary side "pick up" the change in magnetic field in the core and produce a current pulse on the secondary side of the PSU.

Now, as the PSU is loaded more, the PWM IC keeps the voltage on the output the same by sending longer PWM pulses to the transistors on the primary side. This makes the transistors stay in the ON state for a longer period of time, which means the current pulses going through the primary winding on the transformer also become longer and the magnetic field in the transformer core increases proportionately... but only up to a point. Once it reaches saturation, the impedance on the primary side can decrease greatly. And when that happens, the primary transistors will be trying to drive a short circuit pretty much. The Mr. Kaboom follows

Anyways, for your typical half-bridge SMPS with a 33-size EE/EI transformer cores, you're looking at about 300 Watts maximum DC output before things start to get "out of control" with the transformer core saturating.

[PeteS in CA]

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

As long as a core's magnetic properties are active, the transformer primary acts as an inductor rather than a simple wire (= short circuit). The core loses its magnetic properties under two conditions: the magnetic field is too great (saturation); the core gets too hot (~200C for power transformer ferrites, the Curie temperature).

When either happens the primary becomes a short circuit (maybe a couple of tenths of an ohm) and the transistors or MOSFETs swiftly become molten silicon, with the likelihood of a bright flash, a bad odor, smoke, and plastic shrapnel.

[momaka]

GenMax 400 Watt ATX Switching Power Supply

Are low quality power supplies really gone for good now? Or is this thread just being forgotten?

Well, I think we can safely assume the latter, so here goes another low quality power supply: the GenMax [TM] ATX Switching Power Supply.


This gem from 2007 boasts 400 Watts on its label and apparently can also come in 350-Watt, 450-Watt, and 500-Watt variants. Sounds very promising! Let’s see the label.


Oh yes! We get 22 Amps for the 3.3V rail, 28 Amps for the 5V rail, and 14 Amps for the 12V rail. No need to worry ourselves with combined power ratings, though. I’m sure this PSU is solid (it really is! Not leaking or vaporizing… yet. ) And look! – label states this PSU is ATX v2.03 compliant too. Great!!!
…
Okay, okay. Leaving the silly sarcasm aside, let’s go down to the guts. As always, here is a top view. Viewer discretion is advised!


Not sure where to start here as there isn’t much to talk about. This is just another low quality PSU based on the much dated half-bridge design. PWM controller is a 7500B chip and my guess would be most protections (if any) are handled by the 339 quad comparator IC. The main transformer looks like the typical EE/EI 33 size found in many low-end PSUs. Likewise, the 5VSB and BJT drive transformers are also quite small. Both the input and output wires are 20 AWG, with the small difference that the input wires are rated for 600 Volts and have a UL number. As for output connectors: all this PSU has is a 20+4 pin motherboard connector, a 4-pin CPU power connector, 4 peripheral plugs, 1 floppy, and a single SATA power connector. That is just enough to make this PSU usable (i.e. dangerous for your hardware). Those of you with sharp eyes might also have spotted the funny grounding scheme of this PSU, with one of the PCB screws also holding down the grounding wire. And if things weren’t cheesy enough for you (or corny if you like, or… well, not beefy for sure), then there is always the pathetic heatsinks to look at. Here is a better shot of that:


In the above shot we also see the text “WW-86250 REV:2309-A1 PCB” printed on the PCB. Can anyone tell who this PSU is made by? Because I have no clue.
(Side thought: I wonder if the manufacturer really made 2309 revisions of this PSU. Makes sense, though. Otherwise, how else would they get the PSU so gutless and still “working” - probably some major trial-and-error on their part. )

Speaking of gutless, look at the secondary side filtering (or rather, the lack of it):

We get the awesome “one cap per rail” treatment, no PI coils, and… this is my favorite : dummy load resistors in spots marked for additional output filter caps!

The solder side doesn’t look that good either.

https://www.badcaps.net/forum/attachment.php?attachmentid=142174&stc=1&d=1475344632

As you can see, there are quite a few sloppy solder joints. Surprisingly, I do not recall seeing any loose solder balls around… unlike that crappy Raidmax RX-380K (Sun Pro KY-480ATX) I showed a while back, which looked like someone dropped the PCB in a bucket of hot solder from a height of a 10-story building.

Last but not least, the fan:

No idea who the manufacturer is, but at least the label is honest enough to say that it is a sleeve bearing fan. Rated for 0.22 Amps at 12V.

Anyways here is a more detailed look at the components used in this PSU, starting with the primary side and then moving onto the secondary.

Primary Side…
* 250V glass fuse (can’t see rating)
* NTC thermistor (MF72 5D9)
* no input filtering of any kind other than two 1000 pF blue ceramic caps rated for 2 kV (not Y2-class safety approved)
* four RL207 diodes (rated for 2 Amps) for the bridge rectifier
* two primary caps in series: KYS “ROHS VENT”, 200V, 330 uF, 18 mm dia x 36 mm height (measured capacity showed 166 uF and 170 uF on the ESR-micro v4)
* two generic 13007 NPN BJT transistors (by SXW?) for the h-bridge main supply
* one 13003 NPN BJT for the 2-transistor 5VSB circuit
* two KYS “ROHS VENT”, 50V, 10 uF, 5x11 mm (dia x h) - BJT drive caps
* one KYS “ROHS VENT”, 50V, 10 uF, 5x11 mm (dia x h) - “critical” cap for 5VSB

And another picture of the primary side from a different angle:

https://www.badcaps.net/forum/attachment.php?attachmentid=142176&stc=1&d=1475344632

Secondary Side…
3.3 V rail (mag-amp regulated):
* SBL1640CT schottky rectifier (16 A, 40 V, TO-220AB)
* one KYS “CD288”, 10 V, 1000 uF, 10x16 mm cap, no PI coil
* 15-Ohm, 3 Watt load resistor (dissipates 0.726 Watts @ 3.3V)

5 V rail:
* SBL2040CT schottky rectifier (20 A, 40 V, TO-220AB)
* one KYS “CD288”, 10 V, 1000 uF, 10x16 mm cap, no PI coil
* one empty cap spot, 8 mm dia
* 15-Ohm, 3 Watt load resistor (dissipates 1.666 Watts (!) @ 5V)

12 V rail:
* PEC UR1002FCT fast recovery rectifier (equivalent to UF1002FCT…10 A, 100 V, TO-220 isolated)
* one KYS “CD288”, 16 V, 1000 uF, 10x20 mm cap, no PI coil
* one empty cap spot, 8 mm dia
* 270-Ohm, 1 Watt load resistor (dissipates 0.533 Watts @ 12V)

-12 V rail:
* two FR104 fast recovery diodes (1 A, 400 V)
* one KYS “CD288”, 16 V, 330 uF, 8x14 mm cap, no PI coil
* 150-Ohm, 2 Watt load resistor (dissipates 0.96 Watts (!) @ 12V)

-5 V rail:
* two FR104 fast recovery diodes (1 A, 400 V)
* one KYS “CD288”, 10 V, 330 uF, 8x14 mm cap, no PI coil
* 51-Ohm, 2 Watt load resistor (dissipates ~0.5 Watts @ 5V)

5 VSB rail:
* FR302 fast recovery diode (3 A, 100 V)
* one KYS “CD288”, 10 V, 1000 uF, 10x16 mm cap, no PI coil
* one KYS “ROHS VENT”, 10 V, 220 uF, 6.3x11 mm cap, no PI coil
* 51-Ohm, 2 Watt load resistor (dissipates ~0.5 Watts @ 5V)

And here is a shot of the rectifiers bolted onto the secondary heatsink:

https://www.badcaps.net/forum/attachment.php?attachmentid=142177&stc=1&d=1475344632

So all of that above is supposed to be capable of 400 Watts . Well folks, not today!
(Makes one wonder if and/or how much more skimpy the 350 Watt version is.)

You reached the end of my post – congrats!

[Wester547]

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

Wow, what a pile of trash. I give it no more than 200W, but that's without the ripple voltage or voltage regulation in spec. Thanks for the thorough breakdown. I can't seem to find anything about UR1002CT, though. The datasheet I can find for UF1002CT describes it to be a 10A ultrafast and not 16A. The datecode I can see on the label says March 2006 - "Month 3" "2006".

EDIT: Okay, I figured there was another year on the end of the label not visible in the picture. March 2007 then.

[momaka]

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

I can't seem to find anything about UR1002CT, though. The datasheet I can find for UF1002CT describes it to be a 10A ultrafast and not 16A.

Yes, it's a 10A part, sorry. Fixed that typo in time this time . Thanks!
(Copy-pasta mistake, as I reused another post to make the body of this post.)

The datecode I can see on the label says March 2006 - "Month 3" "2006".

There's also a box with "2007" text on the label (supposedly right next to the "2006" text), but it got torn off. The 2007 text was crossed off with a pen, so that suggests this PSU was made in 2007.

Thanks for the thorough breakdown.

You're welcome!

[ChaosLegionnaire]

Re: GenMax 400 Watt ATX Switching Power Supply

Makes one wonder if and/or how much more skimpy the 350 Watt version is.

lol skimpy? this 400w version is already skimpy. the 350w version would probably be nude, the 450w version barely clothed and the 500w version still considered inappropriate for certain conservative countries!

so i am going to reiterate my post that was in another topic:

errr why would u be calling this psu a cutie? it aint exactly a chick! even if it was, her body is cheap, her clothes (labels) are cheap, her insides and her head are all empty and her fans? well... she has none to speak of. i'd put a paper bag over her head anyday...

[forza764]

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

Question: Can a bigger 12v/5v output inductor lower the ripple in cheap psus?

[momaka]

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

Question: Can a bigger 12v/5v output inductor lower the ripple in cheap psus?

Possibly... if it has more turns for each rail (i.e. higher inductance).
A bigger toroid inductor should definitely allow for higher power output, though. Or at least somewhat higher (the wires of the big inductor also need to be thicker, otherwise it may be just as capable as a smaller ones).

lol skimpy? this 400w version is already skimpy. the 350w version would probably be nude, the 450w version barely clothed and the 500w version still considered inappropriate for certain conservative countries!

The content of this website is not available in your country.
(like those stupid YouTube blockers.)

[TechGeek]

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

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