what's this toroidal coil for?

[jpdoe]

I would appreciate if someone would tell me what's the function of the toroidal coil whose core is yellow in this picture. This coil is usually missing in most cheap PSUs, although the PCB has its position silkscreened.
As you can see, this PSU doesn't seem to have PI output filters. It lacks the inductances. The output capacitors are very small also. Only 1000uf.

This is a Noganet branded PSU, model ATX 550P4. Noganet imports into Argentina a huge lineup of cheap chinese products. Quality is hit and miss, since they compete by price. In PSUs, they usually miss. They have only about three PSU models, and this is the most expensive. About usd45 retail. It's the only relatively cheap PSU in Argentina that I know it has passive PFC.

[linuxguru]

Re: what's this toroidal coil for?

That 550 Watt rating is fake - honestly rated, this PSU is between 180 and 250 W. Regarding the yellow-cored inductor, it depends on the schematic. Some PSUs use a saturating-core inductor to derive +3.3V from +5V, but that may not be the case here. Try to reverse-engineer the schematic and post it here - it may shed some light.

[momaka]

Re: what's this toroidal coil for?

I've observed a lot of L&C/Deer PSUs, and this closely resembles one, but with more and beefier components (hey at least you have input filtering ). I'm almost 100% sure that it's also group regulated. Therefore, it's very likely that the big torodial coil at the top-left corner of the first picture is for 5v/12v filtering and the yellow coil to the right is for 3.3v filtering.

What I'm more worried about, though, are the capacitors on the secondary side (particularly the brand). Also, 2000uF total for each output just doesn't seem enough, especially when you consider that there are no PI output filters .

Other than that, it looks a-okay for a 150-250w PSU as linuxguru said. Definetly not a 550 watt PSU though. Although for $45 USD, this PSU should have at least employed mid grade caps like Teapo/Ost/CapXon with twice the uF rating.

[kikkoman]

Re: what's this toroidal coil for?

that thing is the inductor for the passive PFC.

[jpdoe]

Re: what's this toroidal coil for?

@linuxguru: I have this PSU in the system I'm using daily. I will repair a beefier PSU with vented 5vsb output caps, and I'll use it to replace this Noganet unit. When I have it out of the case I'll sure check how the inductor is wired and post it here.

@mokama: I also have the feeling this is a Deer unit. Besides, argentinian importers love Deer. Regarding the capacitors, all of them are BH (Bor Hurng), except for a few green ones, marked HQ or something similar. The BH are CD288 series. I found the datasheet in http://www.huaxinyf.com/en. It seems these 1000uf 10v caps specs are: 1040mA ripple, 0.075ohm impedance.

This PSU has been powering for about 5 months an athlon xp 2000+ with two sticks of ddr memory at 266MHz, an ATI 9600xt and a couple of IDE devices. With the summer approaching, the system is beginning to act out now and then. Its quite wierd, and I want to rule out the PSU as a source of problems. Sometimes, when I want to view a movie, the media player (zoomplayer) doesn't respond. All it takes to make things back to normal is to kill a couple of programs, so that the 2nd RAM stick isn't used.

[jpdoe]

Re: what's this toroidal coil for?

@kikkoman: thanks for your input, but I mean the medium sized toroidal coil soldered to the PCB, next to the big toroidal core, right by the output capacitors. I'll edit the original post to be more clear.

PS: Oops... I just realized i can't edit the first post anymore.

[Krankshaft]

Re: what's this toroidal coil for?

The big coil with the 2 different colored windings is for filtering the 12 volt and 5 volt rails the smaller one next to it is probably for the 3.3v rail.

[zandrax]

Re: what's this toroidal coil for?

This PSU has been powering for about 5 months an athlon xp 2000+ with two sticks of ddr memory at 266MHz, an ATI 9600xt and a couple of IDE devices. With the summer approaching, the system is beginning to act out now and then. Its quite wierd, and I want to rule out the PSU as a source of problems. Sometimes, when I want to view a movie, the media player (zoomplayer) doesn't respond. All it takes to make things back to normal is to kill a couple of programs, so that the 2nd RAM stick isn't used.

Check motherboard caps too: there is a chance they're bad if the mobo acts strangely. Do plugging USB devices or defragmenting the disk crash the computer too?

Zandrax

[jpdoe]

Re: what's this toroidal coil for?

@zandrax: the usb ports work fine. Neither the digital camera nor the pendrive give me problems. I almost never defragment the hard disk, so I don't know about that one. The motherboard is an MSI with good caps. I don't remember if they are nichicon or chemicon... I'll check next time I open the box.

@Krankshaft: Thanks for the info.