What's the cap for?

[Behemot]

I am not sure what the red foil cap is in this PSU for.

It is connected between phase and neutral in front of the bridge rectifier so it behaves like filtration cap continuously (like it's not part of the voltage doubler or something). So it should be safety X, shouldn't it?

[budm]

Re: What's the cap for?

If it is connected across, then yes, it should be safety cap type. There is no X/Y printing on the body of the cap? What is the brand of this power supply, if it has CE then it is faked CE, no way it could have pass CE compliance, all the safety components have to be on the construction listing.

[SIDMX]

Re: What's the cap for?

Yeah it should be an X cap, seems to be 1uF maybe these diped film caps are cheaper than the X ones but im not sure I've never bought diped film caps or maybe they run out of X caps and just put whatever they had on hand, at least it seems to be sitting after the fuse so in the rare event that the cap shorts the fuse must blow. There is a thread on this topic somehow you missed that part

[c_hegge]

Re: What's the cap for?

What PSU is that? It looks like a Delta, but surely, Delta would know better than that?!

[budm]

Re: What's the cap for?

They do make X cap in that type:
[Class%20X2].pdf

[Behemot]

Re: What's the cap for?

It's Delta OEM design, GPS-400AB-C as Thermaltake Litepower 400 PP (W0161).

Now I am looking at it, it is not between phase and neutral, it is on the phase only, in parallel with the passive PFC coil. So possibly it is to shift back the phase change the coil makes? Usually the caps is on the coil itself but not here. Than there is current at high voltage flowing through the cap, but if it fails shorted, the PFC will just not work, not supressing the harmonic distortion, that's all…

[goodpsusearch]

Re: What's the cap for?

Yeah, I have seen this several times, a non safety cap in parallel with PPFC coil.

I attach 4 images with the model of the psu in filename.

[Behemot]

Re: What's the cap for?

Seems to me Delta has very deteriorated in quality. Few years ago, it was able to survive eternity with even the worst crapacitors. But a colleague of mine has informed me (under the preview which just came out) he has the original Delta on this platform, a DPS-300AB-C. After five years, all crapxon capacitors are supposedly bloated.

[c_hegge]

Re: What's the cap for?

^
Or the capxon capacitors have gone down in quality over the last five years and can no longer survive even in Delta power supplies now.

Interestingly, I've only ever seen capxon fail twice in Delta PSUs, and one of those times was because the fan quit after getting badly rusted by the salty coastal environment. The other one only had one cap fail, and it was covered over by wires.

EDIT: I've never seen any other band of capacitor fail in a Delta either. Ltecs and Taicons seem to hold up well in Delta power supplies.

[Behemot]

Re: What's the cap for?

Yeah even those can handle and I don't put ltec above crapxon. I don't know the series used but the older ones were crappier than the newer ones…

[Agent24]

Re: What's the cap for?

CapXon are just crap, simple answer!

[Behemot]

Re: What's the cap for?

So is ltec and taicon…

[c_hegge]

Re: What's the cap for?

^
They aren't great, but capxon is easily worse than either of those two.

btw, Taicon aren't that bad these days, Nichicon's influence over them seems to have helped them to get their act together.

[Behemot]

Re: What's the cap for?

I will consider them good as soon as they got to the level of Nichicon, until than it's just another average crap.

[Agent24]

Re: What's the cap for?

Well, I have not come across a blown Taicon so far, and I have seen LCD monitors where the CapXon are all blown and the Taicons tested fine for ESR, so I figure they must be better quality.

I still replaced the lot though, just in case, but keep the Taicon for testing etc

[Wester547]

Re: What's the cap for?

Yeah even those can handle and I don't put ltec above crapxon. I don't know the series used but the older ones were crappier than the newer ones…

If you're referencing LTEC, their general purpose series (TK, TH, ST) seem to do much worse than their low ESR series (LZx for an example, though their very low ESR series don't seem to hold up well). I think there are threads here that show a 100uF TH often to be the culprit in those 800W SFF Deltas. They seem to dry out as fast as the 8mm Teapos do. And I think your mileage with Taicon also varies with the series. Their lower ESR series (Hx) aren't very reliable but their entry level ESR series seem to do much better (Px), have not actually come across a failed one besides ones exposed to discolorating temperatures (except one bad batch I think). As for CapXon... they are bad enough to fail on the shelf so that should give you a lucid idea of their quality. If Delta really has declined in quality, though, I'd guess that a less aggressive fan controller is the reason.

[Pentium4]

Re: What's the cap for?

I rarely see any failed caps in Delta PSU's as well. Of course, even Delta can't save the impending doom of CapXon on the 5VSB. However, I've seen TONS of failed Ltec TK in Delta PSU's. For the record:
Taicon>Ltec>CapXon

[Behemot]

Re: What's the cap for?

I wonder what topology is this or why there are 8A/900V transistors. It's not push-pull for sure (so no 2x Vin), there is no center-tap. It's also not a half-bridge, there are no foil capacitors. Both drains are connected together (to first transformer pin), both sources are connected together (to V-), gates are separate but I read 66 ohms between them. Second transformer pin is on V+.

It's flyback isn't it.