Is this power supply fake?

[zapta]

I am looking for a 12V power supply for a 3D printer and found this one http://amzn.com/B007K2H0GI . Price is reasonable, it's from a known brand and supposed to have UL approval.

Is it possible to tell if it is fake or not?  Do they come with that hologram UL sticker? Is it possible to tell by looking inside, components quality, etc?



Thanks,

Zapta

[wraper]

Respectable manufacturer, who sometimes got faked. There are no any holograms, more than that holograms stating quality are used on knockoffs more often than on quality gear. Like on this fake flux (no holograms on genuine) http://www.ebay.com/itm/1pc-10cc-AMTECH-NC-559-ASM-BGA-PCB-SMT-IC-Reballing-Soldering-Paste-Flux-Grease-/170878731760?pt=LH_DefaultDomain_0&hash=item27c92a85f0 Photo looks like genuine but it doesn't mean that it is photo of the actual product sold. IMO you won't get fake unless buy extremely cheap on ebay.

[mcinque]

Well, I think the best way to know if that PSU is counterfeit or genuine, it's to contact directly the manufacturer http://www.meanwell.com/
At least, this is what I do in this cases.

[wraper]

You can check if weight is the same 1.07 kg as in the datasheet. Most of the electrolytic capacitors likely will be capxon and rubycon.

[kxenos]

I use them in my systems. I've repaired hundreds of MW supplies. The PS on the photo is 100% a genuine MW power supply. Now if you get what is pictured is a different question but I think it should be OK. These PSs are not that expensive anyway

[NiHaoMike]

Just buy a good quality ATX PSU.

[kwallen]

Just buy a good quality ATX PSU.

ATX power supplies really can't be beat for 12v, and if you buy a modular one you won't have to worry about a massive swathe of cables you need to bundle up out of the way. High current, good protection, and most of the time cheaper than a purpose built supply. I shorted one recently and fully expected it to explode the cables in my face, turns out it has polyfuses though, very neat.

[zapta]

ATX power supplies really can't be beat for 12v, and if you buy a modular one you won't have to worry about a massive swathe of cables you need to bundle up out of the way. High current, good protection, and most of the time cheaper than a purpose built supply. I shorted one recently and fully expected it to explode the cables in my face, turns out it has polyfuses though, very neat.

Yes, I wanted to avoid all those cables. What is a modular one?

[nowlan]

Modular psu let you remove the cable you dont need in your computer. Although you pay a premium for it.
eg, http://www.corsair.com/en/power-supply-units/popular-power-supply-units/modular-psus

[zapta]

Modular psu let you remove the cable you dont need in your computer. Although you pay a premium for it.
eg, http://www.corsair.com/en/power-supply-units/popular-power-supply-units/modular-psus

Never heard of it before. It looks nice, though expensive. I just need the +12V. BTW, do ATX power supplies cut with max current per output voltage or just the aggregated power?  (again, I care only about the 12V current capabilities).

[kwallen]

Modular psu let you remove the cable you dont need in your computer. Although you pay a premium for it.
eg, http://www.corsair.com/en/power-supply-units/popular-power-supply-units/modular-psus

Never heard of it before. It looks nice, though expensive. I just need the +12V. BTW, do ATX power supplies cut with max current per output voltage or just the aggregated power?  (again, I care only about the 12V current capabilities).

They usually have a maximum rating for the whole supply, and an isolated one just for the 12v rail. Computers now mainly use the 12v rail for the CPU supplied and graphics cards so you can often draw the entire rating of the power supply just on that. Most will have a similar label as the one below, the lower rating is for the maximum cumulative load and the upper ones are a break down of the maximum for each rail. I've found that they don't care about drawing full loadings on one output, just be careful not to go over the ratings of the molex connectors on the output or they will ignite (use multiple runs from the supply and gang them up externally).




The one trick you need to know when using them is that there is a power enable pin that you need to short to ground to get the power supplies to start up. People often do it with a paperclip as a temporary thing, but they're cheap enough for generic supplies that you can just cut up this harness and build a switch into it yourself if you'd like.

[wraper]

Don't think that PC PSU is any good for this purpose. Not only they are more than two times bigger but also very thick compared to this MW one. Therefore much thicker enclosure is needed. Some of them also have a problem to work normally when other power rails stay without any load. As of modular PSUs, there will be a lot of permanent wires in addition to detachable ones anyway. Just don't see any reason to use ATX, no price, no size, no reliability advantage. That would change drastically if you would need something in 1000+W realm.

[zapta]

Don't think that PC PSU is any good for this purpose. Not only they are more than two times bigger but also very thick compared to this MW one. Therefore much thicker enclosure is needed. Some of them also have a problem to work normally when other power rails stay without any load. As of modular PSUs, there will be a lot of permanent wires in addition to detachable ones anyway. Just don't see any reason to use ATX, no price, no size, no reliability advantage. That would change drastically if you would need something in 1000+W realm.

Do all modular ATX PSU come with a permanent wire harness in addition to the chassis connectors?  It's hard to see in some product pictures (probably intentionally so they look better).

The main advantage I see in ATX PSUs is that they come with a standard mains connector and a on/off switch(?).  My top candidate now is this MW 12VDC 200W which is available locally from a reputable vendor. The part I don't like is the exposed mains connection and the fact that I need to add a mains switch somewhere. (it does have a remote control input but it requires external power, I think(?)).

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_194774_-1



BTW, this power supply is for this 3D printer kit. The manual says that it needs up to 11amp so 200W will have some margin for future upgrades.

http://www.makerfarm.com/index.php/prusa-8-i3v-kit-v-slot-extrusion.html/


Edit: found this on eBay. It can take care of the connector + switch thing. Will look for something more reputable at DigiKey.

[kwallen]

Do all modular ATX PSU come with a permanent wire harness in addition to the chassis connectors?  It's hard to see in some product pictures (probably intentionally so they look better).

Depends on the supply. I have ones that don't and ones that do.

Don't think that PC PSU is any good for this purpose. Not only they are more than two times bigger but also very thick compared to this MW one. Therefore much thicker enclosure is needed. Some of them also have a problem to work normally when other power rails stay without any load. As of modular PSUs, there will be a lot of permanent wires in addition to detachable ones anyway. Just don't see any reason to use ATX, no price, no size, no reliability advantage. That would change drastically if you would need something in 1000+W realm.

They are objectively safer though, even just from the standpoint of not having to mess about with mains voltages at all.

[zapta]

Anybody knows reputable manufacturer of module ATX PSU's (with connector only outputs)?  I prefer to have a safe product with UL and such.

Edit: I just leaned that modular ATX PSU with output connectors only are called 'fully modular'.

[Rasz]

get ANY ATX psu (even used one), and just cut cables you dont plan to use

[wraper]

One more thing to consider, if this PSU is supposed to work at zero load (heater off and no other load at all), ATX psu is a very bad choice. Many of them will just not start at all, short fan spin up and instant shutdown. That MW one have load resistors inside, therefore zero load is not an issue.

[rolycat]

Seasonic, Corsair and Antec are all top-rank manufacturers with full-modular power supply offerings - Seasonic are the OEM for a number of Corsair and Antec branded PSUs.

The Seasonic SS-620GM2 offers 48A on the 12V rail for around $100.

[NiHaoMike]

One more thing to consider, if this PSU is supposed to work at zero load (heater off and no other load at all), ATX psu is a very bad choice. Many of them will just not start at all, short fan spin up and instant shutdown. That MW one have load resistors inside, therefore zero load is not an issue.

The "Haswell-ready" PSUs are specifically designed to operate down to no load. Also, I haven't come across a good quality PSU that won't operate without a load.

[zapta]

The Seasonic SS-620GM2 offers 48A on the 12V rail for around $100.

Thanks rolycat. this one is not fully modular, right?

Is the 550w here any good? It has cTUVus, TUV, CB certification but not UL and has good reviews on amazon http://amzn.com/B00FIYI42Y

http://www.firepower-technology.com/product-listings/fatal1ty-product-family/
http://www.firepower-technology.com/firepower/fp/wp-content/uploads/FTY-SPECIFICATION2.pdf

[rolycat]

The Seasonic SS-620GM2 offers 48A on the 12V rail for around $100.

Thanks rolycat. this one is not fully modular, right?

It is fully modular - details here. There's one for sale here for $75.

Here is a review of the hybrid modular variant - the M12II-620, which should give an idea of the quality.

Is the 550w here any good? It has cTUVus, TUV, CB certification but not UL and has good reviews on amazon http://amzn.com/B00FIYI42Y

FirePower took over OCZ's PSU offerings, including various PC Power & Cooling units. There's a review here - they aren't terribly complimentary about the build quality.

[wraper]

One more thing to consider, if this PSU is supposed to work at zero load (heater off and no other load at all), ATX psu is a very bad choice. Many of them will just not start at all, short fan spin up and instant shutdown. That MW one have load resistors inside, therefore zero load is not an issue.

The "Haswell-ready" PSUs are specifically designed to operate down to no load. Also, I haven't come across a good quality PSU that won't operate without a load.

My 1000W chieftec won't start for example, it is 4 years old, certainly not a cheap junk. As I repaired some computer PSUs, was checking them without any load attached. And most of them even if working, certainly do not like no load (emitting strange sounds, being unstable).

[DanielS]

My 1000W chieftec won't start for example, it is 4 years old, certainly not a cheap junk. As I repaired some computer PSUs, was checking them without any load attached. And most of them even if working, certainly do not like no load (emitting strange sounds, being unstable).

Every crappy PSU I have ever owned or repaired worked fine "without load" because they have internal shunt resistors providing that absolute minimum amount of load they need to keep running without going out of bounds. Things get more complicated when you throw cross-loading at group-regulated units without putting some extra load on other outputs.

Modern high-end, high-efficiency PSUs have a single 12V primary rail and provide other outputs from secondary DC-DC converters. The DC-DC converters provide the 12V rail's minimum load and the secondary rails require practically no load at all since they do not need to sink the primary transformer's leakage inductance.

[LabSpokane]

I am looking for a 12V power supply for a 3D printer and found this one http://amzn.com/B007K2H0GI . Price is reasonable, it's from a known brand and supposed to have UL approval.

Is it possible to tell if it is fake or not?  Do they come with that hologram UL sticker? Is it possible to tell by looking inside, components quality,

Thanks,

Zapta

Pass on the Meanwell. You can thank me later.

I'm not sure what amperage you need but you could try a Rhino from Automation Direct:
http://www.automationdirect.com/adc/Shopping/Catalog/Power_Products_(Electrical)/DC_Power_Supplies/5VDC,_12VDC,_48VDC,_DIN_Rail_Mount

You can find a ton of used industrial power supplies on ebay that are better than what you're looking at. Phoenix and Sola are also very good brands, but are much more expensive than the Rhino new.

[zapta]

The Seasonic SS-620GM2 offers 48A on the 12V rail for around $100.

Thanks for the pointer. I just order one from Amazon 

(SuperBiiz is local but has 'F' BBB rating).

[zapta]

The Seasonic 620W arrived today. It has a slick black case with connectors only. I had to short that switch signal to ground to get it started. The fan is  very quite and I had no problem to get 200W out of a 12V connector (my electronic load goes up to 200W).  Open voltage was 12.1 volt and at 200W it went down to 11.V (measured directly on the connector, a little bit less at the electronic load).

The only down side is that these ATX power supplies have very specific mounting holes and are not general bracket friendly.

Thanks everybody for the information.  The 3D printer kit will arrive on Tuesday.

[LabSpokane]

Open voltage was 12.1 volt and at 200W it went down to 11.V (measured directly on the connector, a little bit less at the electronic load).

You do realize that the load regulation of that supply is absolute crap, right?  Even a bargain basement DIN rail supply is rated at 2% - and will meet the spec.

[ajb]

If you examine the cables that came with your power supply you might be able to identify some sense wires for the 12V rails.  Connecting them up ought to give you better regulation.

[zapta]

If you examine the cables that came with your power supply you might be able to identify some sense wires for the 12V rails.  Connecting them up ought to give you better regulation.

I will give it a try. I sued my own 4x2 mini fit cable with parallel beefy wires and measured the voltage directly on the output connector of the PSU. Do you expect the stock wires to have voltage sense? If not, why do you expect them to give better results?

[Rasz]

Do you expect the stock wires to have voltage sense? If not, why do you expect them to give better results?

yes, 12v line has separate sense wire on ATX connector

[zapta]

Do you expect the stock wires to have voltage sense? If not, why do you expect them to give better results?

yes, 12v line has separate sense wire on ATX connector

Ok, that's make sense, though I would expect that the voltage sense will not just be open but also connected with internal resistors to the power out points of the unit which is the point where I measured the voltage.

[zapta]

I just measured resistance between the pins of one of the 12V output connector. All four (+) pins have perfect short and so all the four (-) pins.  Doesn't look like it has voltage sensing.

[wraper]

Seems that what I said is happening now. Try to put some load (at least 0.5A, more is better) on the 5V rail. Pretty sure that load regulation on 12V rail will return to normal.

[zapta]

Seems that what I said is happening now. Try to put some load (at least 0.5A, more is better) on the 5V rail. Pretty sure that load regulation on 12V rail will return to normal.

Thanks. I will give it a try and will report here.

[Psi]

ATX power supplies really can't be beat for 12v, and if you buy a modular one you won't have to worry about a massive swathe of cables you need to bundle up out of the way. High current, good protection, and most of the time cheaper than a purpose built supply. I shorted one recently and fully expected it to explode the cables in my face, turns out it has polyfuses though, very neat.

heh, i've seen what happens when they don't have a polyfuse, its not pretty.
PSU is usually fine, but the cables all turn into horrible thick smoke for a few seconds until you get a direct short as wires melt into each other and the chip shuts down from overcurrent.

[wraper]

Just buy a good quality ATX PSU.

ATX power supplies really can't be beat for 12v, and if you buy a modular one you won't have to worry about a massive swathe of cables you need to bundle up out of the way. High current, good protection, and most of the time cheaper than a purpose built supply. I shorted one recently and fully expected it to explode the cables in my face, turns out it has polyfuses though, very neat.

Where did you see polyfuses in ATX psu? There is overcurrent protection if it is not complete junk but no polyfuses. Just imagine a size of the PTC holdling a few dozens of amperes. Moreover they are so slow that everything will fail before it trips.

[zapta]

Seems that what I said is happening now. Try to put some load (at least 0.5A, more is better) on the 5V rail. Pretty sure that load regulation on 12V rail will return to normal.

Yes, you are right, I connected a  7.5ohm resistor to the 5V and the 12V rail is now at 11.875V on the load at 16A. Much better.

Not sure if I like this power supply. I may get a real one.

[a210210200]

Seasonic ATX power supplies are generally good quality stuff,

Is this the power supply you have?
http://www.hardocp.com/article/2010/05/18/seasonic_m12ii620_power_supply_review/2

It is noted for not being the best in voltage regulation and is an older design.

Most good quality ATX power supplies have short circuit protection which isn't just a polyfuse as it acts basically instantly and is usually digitally controlled circuit that cuts off the entire supply if it detects a short circuit or other trip event (If you have thousands of dollars of equipment plugged into a power supply you don't want a not fully seated card or DIMM melt the motherboard sockets). They also have low noise optimized fan curves as some power supplies don't even run the fan if your not drawing power and smoothly ramp up with load/temperature unlike some industrial psus which either have a on/off thermostatic or really loud fan.

[HackedFridgeMagnet]

Pass on the Meanwell. You can thank me later.

Don't post nonsense like that. How can he thank you later?

Back up what you say with some reasoning, reference or experience, or state that it is just a random opinion or even easier don't say anything at all.

[zapta]

Seasonic ATX power supplies are generally good quality stuff,

Is this the power supply you have?
http://www.hardocp.com/article/2010/05/18/seasonic_m12ii620_power_supply_review/2

It is noted for not being the best in voltage regulation and is an older design.

Most good quality ATX power supplies have short circuit protection which isn't just a polyfuse as it acts basically instantly and is usually digitally controlled circuit that cuts off the entire supply if it detects a short circuit or other trip event (If you have thousands of dollars of equipment plugged into a power supply you don't want a not fully seated card or DIMM melt the motherboard sockets). They also have low noise optimized fan curves as some power supplies don't even run the fan if your not drawing power and smoothly ramp up with load/temperature unlike some industrial psus which either have a on/off thermostatic or really loud fan.

I think I have this one  (their product ids are very confusing, I think they try to appeal to games or something)

http://www.seasonicusa.com/M12II-Bronze.htm

It's quite, has integrated on/off switch and fully modular (that is, not wires coming out of the case, just connectors). The down side is that it requires a 5V power resistor to have decent regulation on the 12V. Also, has a ATX PSU, it has limited mounting options.

[zapta]

Pass on the Meanwell. You can thank me later.

Don't post nonsense like that. How can he thank you later?

He meant well.

;-)

[LabSpokane]

Pass on the Meanwell. You can thank me later.

Don't post nonsense like that. How can he thank you later?

Back up what you say with some reasoning, reference or experience, or state that it is just a random opinion or even easier don't say anything at all.

Is a 100% failure rate enough for you?  I've had to deal with them commercially and replaced EVERY SINGLE ONE at great expense. They may "mean well", but they make shit power supplies.  I'd flat out fire anyone that used a Meanwell in our equipment. It just demonstrates a complete lack of judgement.

Phoenix, Sola, Automation Direct, etc. all make a nice power supply that will meet specs and last.

[a210210200]

Anybody knows reputable manufacturer of module ATX PSU's (with connector only outputs)?  I prefer to have a safe product with UL and such.

Edit: I just leaned that modular ATX PSU with output connectors only are called 'fully modular'.

SFX and TFX supplies are also just different physical form factors and will carry the safety ratings as ATX supplies will. (They are meant for smaller form factor cases).

TFX,

http://www.newegg.ca/Product/Product.aspx?Item=N82E16817151115 (Two rails 12V 200W each, fully modular, review: http://www.hardocp.com/article/2012/04/04/seasonic_ss350tgm_power_supply_review/  )

SFX,

http://www.silverstonetek.com/product_power.php?tno=7&area=en , (Single rail multiple versions, a little off on the regulation side, very tiny, fully modular available) http://www.hardocp.com/article/2014/08/26/silverstone_sfx_sx600g_600w_power_supply_review/9

Since I just like top end stuff I use seasonic atx supplies like this one (They are pricy stuff at that point but fanless at low use and very tight regulation/noise),
http://www.hardocp.com/article/2013/02/04/seasonic_platinum660_660w_power_supply_review/4

(Technically if you put the 3d printer close enough (right beside) to your computer tower you could run it off the 12V PCI-E cabling which are meant to run GPU's drawing hundreds of watts of power at 12V)

Seasonic, Antec, Corsair, ... are all good mfgs. It actually depends sometimes as most companies use a third party to do the design/mfg. Seasonic just happens to be both an OEM and direct sales.

Computer review sites like hardocp have a pretty good computer power supply test suite and cover a lot of supplies. (You want sites that give you internal shots, ripple, efficiency, regulation test results)

Tom's hardware/anandtech also do reviews on computer power supplies as well.
http://www.tomshardware.com/articles/?tag=power-supplies&articleType=review

[TheRevva]

You want a PSU for a Reprap type project...
I'd SERIOUSLY consider looking on 'fleabay' for NOS (New / Old Stock) HP server PSUs.
They're built to last quite a while and, depending on the model, can give you all the current you'd ever want for your heatbed / hotend / stepper motors.

On my Reprap, I ended up using TWO HP PSUs (HP part number 382175-501) that I 'acquired' for free.  (One would have been enough since the 12V rail is rated at 60A max)
SOME of the HP server supplies don't have all the output rails of a traditional ATX supply (and some of them intentionally set their output a couple hundred millivolts high to cater for cable resistance losses)
Here's the first 'fleabay hit' in my search for HP server PSU:
http://www.ebay.com/itm/HP-DL360-DL385-G5-Server-700W-Power-Supply-Unit-411076-001-412211-001-393527-001-/231179762487?pt=US_Server_Power_Supplies&hash=item35d3633b37
US$15.29 will buy you this 700W PSU.
It doesn't have a 5V output at all (the standby output rail is 3V3 @ 3.5A.  Might be useful though if you're using an ARM instead of an Arduino Mega etc.)
The main +12V rail is actually 12.15V @ 56A
It also has a weird 10.5V @ 1.5A standby output too?

Nevertheless, I'd GLADLY run a Reprap from it (inclusive of a decent Mk1a heatbed for ABS printing).

Your post has reminded me...  I must 'make some progress' on my CNC machine.  (Nema23 steppers, PSUs, endmills etc all here, just need to nut out the rest of the physical design)

[HackedFridgeMagnet]

Pass on the Meanwell. You can thank me later.

Don't post nonsense like that. How can he thank you later?

Back up what you say with some reasoning, reference or experience, or state that it is just a random opinion or even easier don't say anything at all.

Is a 100% failure rate enough for you?  I've had to deal with them commercially and replaced EVERY SINGLE ONE at great expense. They may "mean well", but they make shit power supplies.  I'd flat out fire anyone that used a Meanwell in our equipment. It just demonstrates a complete lack of judgement.

Phoenix, Sola, Automation Direct, etc. all make a nice power supply that will meet specs and last.

Sry about the post LabSpokane, I must've been having a bad hair day.

I've only ever had 2 of them, they're working fine. Maybe I don't run them hard enough.
They seem good value for money to me.
How did those supplies fail? How many failed? Did you get warranty?

[LabSpokane]

Pass on the Meanwell. You can thank me later.

Don't post nonsense like that. How can he thank you later?

Back up what you say with some reasoning, reference or experience, or state that it is just a random opinion or even easier don't say anything at all.

Is a 100% failure rate enough for you?  I've had to deal with them commercially and replaced EVERY SINGLE ONE at great expense. They may "mean well", but they make shit power supplies.  I'd flat out fire anyone that used a Meanwell in our equipment. It just demonstrates a complete lack of judgement.

Phoenix, Sola, Automation Direct, etc. all make a nice power supply that will meet specs and last.

Sry about the post LabSpokane, I must've been having a bad hair day.

I've only ever had 2 of them, they're working fine. Maybe I don't run them hard enough.
They seem good value for money to me.
How did those supplies fail? How many failed? Did you get warranty?

No worries. Peace.

I don't have my lab notebook so I don't remember the exact failure mode. We replaced 50-75 of them in the field at our expense. Of course, they were all located on secure, government facilities and the tech had to be escorted, so it was slow, excruciating, and expensive. That was in addition to the internal expenses of changing BOMS, drawings, creating replacement wiring harnesses, fighting management, and profusely apologizing to a great customer for our negligence.

The Meanwells bench tested ok when new at room temp with light loads. Unfortunately, the engineer who spec'ed them out never bothered to put them on a e-load and stuff them into an environmental chamber.  I honestly believe that Meanwell simply copied the data on competitors' spec sheets based on what I saw. 

I didn't pursue warranty because I wouldn't field the replacement units.

MWs are probably fine for light duty in office environments for non-critical work. For commercial work or for times when your time is worth money, there are just so many better choices. Yes, those choices cost more, but they will also last and last. And like was already noted, I think you're far better off buying a good, industrial power supply used off ebay than a new crap one.

[a210210200]

You want a PSU for a Reprap type project...
I'd SERIOUSLY consider looking on 'fleabay' for NOS (New / Old Stock) HP server PSUs.
They're built to last quite a while and, depending on the model, can give you all the current you'd ever want for your heatbed / hotend / stepper motors.

On my Reprap, I ended up using TWO HP PSUs (HP part number 382175-501) that I 'acquired' for free.  (One would have been enough since the 12V rail is rated at 60A max)
SOME of the HP server supplies don't have all the output rails of a traditional ATX supply (and some of them intentionally set their output a couple hundred millivolts high to cater for cable resistance losses)
Here's the first 'fleabay hit' in my search for HP server PSU:
http://www.ebay.com/itm/HP-DL360-DL385-G5-Server-700W-Power-Supply-Unit-411076-001-412211-001-393527-001-/231179762487?pt=US_Server_Power_Supplies&hash=item35d3633b37
US$15.29 will buy you this 700W PSU.
It doesn't have a 5V output at all (the standby output rail is 3V3 @ 3.5A.  Might be useful though if you're using an ARM instead of an Arduino Mega etc.)
The main +12V rail is actually 12.15V @ 56A
It also has a weird 10.5V @ 1.5A standby output too?

Nevertheless, I'd GLADLY run a Reprap from it (inclusive of a decent Mk1a heatbed for ABS printing).

Your post has reminded me...  I must 'make some progress' on my CNC machine.  (Nema23 steppers, PSUs, endmills etc all here, just need to nut out the rest of the physical design)

As long as you don't mind the noise getting a used server power supply may be a good idea they are built much more robustly and if you want you can get N+1 redundant ones. Just most use small ultra-high rpm fans so can make a lot of noise if doesn't have a load/temp ramp.

[TheRevva]

You want a PSU for a Reprap type project...
I'd SERIOUSLY consider looking on 'fleabay' for NOS (New / Old Stock) HP server PSUs.
They're built to last quite a while and, depending on the model, can give you all the current you'd ever want for your heatbed / hotend / stepper motors.

On my Reprap, I ended up using TWO HP PSUs (HP part number 382175-501) that I 'acquired' for free.  (One would have been enough since the 12V rail is rated at 60A max)
SOME of the HP server supplies don't have all the output rails of a traditional ATX supply (and some of them intentionally set their output a couple hundred millivolts high to cater for cable resistance losses)
Here's the first 'fleabay hit' in my search for HP server PSU:
http://www.ebay.com/itm/HP-DL360-DL385-G5-Server-700W-Power-Supply-Unit-411076-001-412211-001-393527-001-/231179762487?pt=US_Server_Power_Supplies&hash=item35d3633b37
US$15.29 will buy you this 700W PSU.
It doesn't have a 5V output at all (the standby output rail is 3V3 @ 3.5A.  Might be useful though if you're using an ARM instead of an Arduino Mega etc.)
The main +12V rail is actually 12.15V @ 56A
It also has a weird 10.5V @ 1.5A standby output too?

Nevertheless, I'd GLADLY run a Reprap from it (inclusive of a decent Mk1a heatbed for ABS printing).

Your post has reminded me...  I must 'make some progress' on my CNC machine.  (Nema23 steppers, PSUs, endmills etc all here, just need to nut out the rest of the physical design)

As long as you don't mind the noise getting a used server power supply may be a good idea they are built much more robustly and if you want you can get N+1 redundant ones. Just most use small ultra-high rpm fans so can make a lot of noise if doesn't have a load/temp ramp.

Granted, MOST server PSUs are, as A21... has mentioned, somewhat louder than your typical ATX desktop CPU. However...
1: We're talking about a Reprap type project here...  I cannot even HEAR mine over the noise of the 5 * Nema17 stepper motors.
2: They're generally FAR more 'reliable' than a typical ATX PSU
The latter point is quite important.  Your heatbed ALONE will be sucking a BIG chunk of 'juice'.  I dare you to take apart almost ANY ATX PSU and then do a quick datahsheet lookup on the dual schottkey diode used for the +12V rail.  You truly have to wonder how the designers kept a straight face in stating that the rail is 'rated' for 500+ Watts when they're using a dual Schottkey rated at a measly 10-20 Amperes.

If you DO go with an ATX, I'd recommend investigating that rectifier (and 'upgrading' it if applicable).  I'd also SERIOUSLY inspect the LOW-ESR output caps at the same time.  (Take a look at some of the 'horror stories' on the badcaps.net forum).  After that, I'd suggest you think seriously about the 'load' that your reprap is placing on the PSU.  The stepper coils are all nice reactive inductors.  Not boring old resistive loads.  Thankfully, the inductance of your heatbed is VERY small (by design).  However, your hotend heater will, quite likely, be another fairly high current inductive load.

P.S.
It's probably a good idea to grab a few spare Power MOSFETS while you're at it.  I let out the smoke from the pair on my RAMPS board several times before I got it right.  (They're no longer mounted on the RAMPS)
Another 'pointer'...  Keep imagining that you're running a 2.4kW heater through every wire you install.  (You're not of course, but you'll thank me in the end)

[zapta]

The Seasonic died today when I accidentally shorted the +12V output. First it stopped working (didn't turn on) and after 10-15 minutes I could turn it on again but it is very noisy and barely gives 1 amp.

Aren't these power supplies suppose to be protected against an output short?

I plan to stop at the store tomorrow and get the ATX power supply recommended by MakerFram. It's not modular but I can rip all the fixed wires I don't need.

http://www.staples.com/Antec-VP-450W-Power-Supply/product_928656

[TheRevva]

The Seasonic died today when I accidentally shorted the +12V output. First it stopped working (didn't turn on) and after 10-15 minutes I could turn it on again but it is very noisy and barely gives 1 amp.

Aren't these power supplies suppose to be protected against an output short?

I plan to stop at the store tomorrow and get the ATX power supply recommended by MakerFram. It's not modular but I can rip all the fixed wires I don't need.

http://www.staples.com/Antec-VP-450W-Power-Supply/product_928656

I'd be mildly apprehensive about running a Reprap on a 450W ATX PSU...
Sure, it probably is 'within spec' (just), but it'd be like running your car engine on the RPM Redline 24/7.
I assume you have a heatbed (for printing ABS).  Generally, these only suck about 10A from the +12V rail.  (Circa 120W)
Your hotend heater can vary HUGELY depending on the design.  I've seen some nichrome wire based heaters trying to pull 20A (240W), but mine only eats 4A (48W).  Let's take a stab at 40W since this is more common.
The only other current drain (of any significance) is all your stepper motors. Generally 4 or 5 Nema 17 steppers.  (X axis, Y axis, 1 or 2 Z axis and a filament feeder)
Assuming you use a decent stepper driver (such as the Allegro A4988) you can easily see 2A peak currents on each winding (albeit for VERY short durations since it tries to keep the AVERAGE current at the set-point)...  However, worst case that still gives 2A * 5 motors * 2 coils per motor = 20A PEAK (240W)

Adding it all up -> Heatbed + Hotend + Motors = 120W + 40W + 240W = 400W peak drain even if you use a whimpy hot end heater like mine!
If I was FORCED to use a 450W PSU, I'd use a PAIR of them.  One for the heatbed and the other for the hotend + steppers.  This is exactly WHY RAMPS boards have separate inputs from PSU(s).  In my case, my RAMPS board only 'sees' the stepper motors since I've mounted the power FETs offboard (after letting out their smoke a few too many times)

What controller design are you using?

[zapta]

@therevva, I am using a stock Makerfarm 8" Prusa I3V. It has a Ramps board with two 12V inputs. According to Coling from Makerfarm, one require 11A and one 5A.  Got the Antec this morning and installed it. The box says it has two 12V rails, each can give 18A or total of 360W on both rails. All the yellow +12V wires are shorted internally in the PSU so I don't understand what they mean by a 'rail' (each has a few connectors), maybe some passive filter inside. I had to load the 5V with a resistor, both 12V rails drop significantly when I load them. It seems to be a good fit for this printer (and recommended by Makerfarm). I may open it and remove all those wires that I don't use.

I saw people taking about using an ATX PSU as a lab bench. Was disappointed by lack of protection against shorts, at least with the Seasonic.

[wraper]

IMO should just bought that MeanWell. Unless in harsh conditions with 24/7 operation, nothing would happen to cheapest model. Different models have different parts too. Cheapest series have capxons in them, more expensive ones Japanese only capacitors. Manufacturer warranty period in the datasheet is quiet different too 1, 2, 3, 5 years. About failures written, you get what you pay for, if you choose cheap PSU for harsh and very demanding conditions, then what you should expect? At least I don't see how MW power supplies can be less reliable than consumer grade ATX power supplies.
P.S.
All those who wrote about new ATX uber technology where rails are separately regulated, DC/DC converters inside  , where did you get that stupid idea from? Maybe in some 1000W+ mega expensive ones, but not in mainstream for sure.

[zapta]

IMO should just bought that MeanWell.

That's was my main choice but having the switch and power connector on the ATX makes things simpler compare to the terminal strip of the main standard power supply. My 3D printer is open frame, no enclosure, and the PSU just sit next to it on the desk.

Here is a leaflet that arrived with the Antec. See how they split the 12V connectors into 'rails'. One could think that they are independently regulated. They are not, the are connected internally, possibly through some passive filter.

[wraper]

Usually you get true separate rails only in high power PSUs which have 2 transformers.

[zapta]

Usually you get true separate rails only in high power PSUs which have 2 transformers.

Do they still require loading of the 5V?

[a210210200]

If a power supply uses DC-DC conversion for minor rails it should be able to handle any mixed load as everything is running off the 12V rail anyways. Most new supplies just use "virtual" rails which are just having multiple over current protection groups each with their own current limit and some PC builders perfer non-ATX spec single rail power supplies that have an obscenely high current limit so that they don't have to think which rail is what when plugging in GPUs. (This only becomes a problem if someone tries to use splitters to say power a couple GPUs off one cable which is a very bad idea)

ATX supplies work fine for 12V and antec also makes good supplies. The only companies I'd really avoid are ones from things like this (Add OCZ which no longer makes power supplies I think and they also went bankrupt and I had a OCZ power supply fail on me as well),

http://www.tomshardware.com/reviews/low-cost-psu-pc-power-supply,2862.html

[zapta]

Here is an interesting solution for the open Mean Well contacts, a 3D printed cover with on/off switch.

http://www.thingiverse.com/thing:40377

Too late for me but the ATX PSU works good and I removed all the extra wires so it looks clean.

Edit: and here is another one, with power connector.