One of the reasons why video card manufacturers recommend 500w+ psus

[mariushm]

Just had the PSU below die in the office where I work, it came bundled with the case and powered a shitty core 2 duo with 8 gb DDR3 and integrated graphics. Office pc used with excel and word.

 

I'm typing this from phone cause I took pics on phone, will switch to PC and edit the post to add more details

 

edit: 

 

So as you can see the power supply claims to be 450w model, but if you look at the voltage that matters the most in modern computers, the label says it can do 12v x 18A = 216 watts 

It also claims up to 20A on 3.3v and 24A on 5v but as you will see from the pictures, that's highly unlikely. 

 

The design is one from the Pentium 3 / Pentium 4 days , with equally old primary transistors (couldn't read the part numbers from them and didn't want to cut myself bending the primary heatsink) and using plain old diodes for secondary rectification. 

The primary switching transformer is that big one between heatsinks and claims to be EER-35 but that's a lie, physically it's too small for such name. I wouldn't trust such small transformer to be capable of more than 200-250 watts in total. 

The stand-by voltage is supplied by that small transformer, the DIP chip to its left and the diode and capacitor to the right. 

 

On the secondary heatsink, you have from left to right:  3.3v rectification,  12v rectification and 5v rectification 

For 3.3v they use a MBR2045 , a 45v  20A diode pack -  https://www.diodes.com/assets/Datasheets/ds31799.pdf - , so in theory the component can rectify 20A of current, provided the transformer can also provide that much power (which it can't, if 5v and 12v are also heavy used)

For 12v, they use a Mospec F16C20C which is actually a 200v 16A diode pack - F16C20C.pdf   - so the component in theory can't even handle the 18A advertised on the label 

It's also worth pointing out that unlike the MBR2045 which was specified for 20A up to 125C, this one is rated for 16A only up to 60C - according to datasheet it must be kept at or below around 70c to be able to rectify 16A of current : 

The heatsink and the fan will cool the component, but the heatsink is quite thin and undersized, and also has to deal with dissipating the heat produced by the 3.3v and 5v rectifiers. So not only it can't do 18A on 12v, it can't even do 16A if you heavily load the power supply, because you won't be able to keep the heatsink at under 70-80c .

 

The 5v rectifier is similar to the 3.3v one, I read the part number but didn't write it down and it's hard to read in the pictures. 

 

The PSU died mainly because of capacitors swelling up - you can see one swollen and the others are probably also dead ... but the actual fault is some diode shorted somewhere - don't see anything blown but the psu won't start (I hear it buzzing so at least it tries to send pulses into the transformer)

 

 

[ZetZet]

Hey, it lasted since core 2 duo days, that's a champion of a power supply. But yeah, the combined wattage is stupid. 

[Stormseeker9]

One of the reasons? This is what a 15 year old psu? Powering next to none (I believe C2D was not power hungry? Could be wrong).

 

besides that, nowadays they recommend 750+W when you want them big boys from Nvidia

[mariushm]

No, the design is from the Core2 duo days ... the psu is maybe 3-4 years old.  The previous IT guy bought some cases that came with power supplies and moved the old hardware into those cases. 

 

But yeah, for a system consuming 50w and runs 8h a day they're acceptable... but regular people don't know these things and just look at the wattage and buy these cheap things.

[PDifolco]

That was a shitty PSU, good ones can deliver full power on the 12v rail