Power supply build quality pictorial. part 2

[Wester547]

Re: Power supply build quality pictorial. part 2

I meant in forward topology, which (because it uses half-wave rectification) only uses 70% of the rectifier's power. If it only uses 70%, could you theoretically use 100% even in forward topology if you pulled that from it?

[ben7]

Re: Power supply build quality pictorial. part 2

Well the rectifier doesn't have a current rating, it would just run hotter and have a shorter lifespan. I imagine if you run a rectifier in excess of its current rating for too long it will simply fail.

They will.

Usually they can stand short overloads.

I once pulled a few amps through a 1N4148 for a few secs ... the damn thing still worked fine after that! (It was made by Fairchild too, I bet a no-name brand one would have failed) It did get mighty hot though! Hot enough to smoke a little; it only was dirt on the diode itself.

[c_hegge]

Re: Power supply build quality pictorial. part 2

It really depends on how well you cool them. If you use tiny heat sinks and let the rectifier heat up to 100+ *C, you'll be hard pressed getting 70% of it's rating. If you give it big heat sinks and keep it cool and pulling its rating won't be a problem.

[Wester547]

Re: Power supply build quality pictorial. part 2

But in forward topology, through half-wave rectification and the other diode acting as a flyback, it's said that only 70% of the full rectifier is used... assuming that you have a decent heatsink and an 80mm, temperature-controlled fan, even though only 70% is used via that topology, could you push it to use more anyway?

[c_hegge]

Re: Power supply build quality pictorial. part 2

^
Yes. The datasheet rating is what the rectifier can handle if you let it heat up to 120*C (or whatever the maximum specified temperature is). Although it's not specified in the datasheet, a 20A rectifier can probably handle 25A or even 30A if kept cool, so then you'd assume 70% of 30A, which would be 21A. I've done it before for sustained periods without incident.

[Wester547]

Re: Power supply build quality pictorial. part 2

In some datasheets, though, they all say "TC", "TA", or "TJ" 25C unless otherwise specified/stated when they give the table of specifications that includes the maximum limit of the rectifier. I've seen that everywhere from TO-247 parts from STMicroelectronics to TO-220 parts from Fairchild Semiconductor. Of course, they didn't (unless they give a comparison to heatsink temperature) put it on a heatsink or run a fan over it, so you're right. However, as ben7 demonstrated, the rectifier still has a limit that should not be exceeded (by double fold, at least) even with good cooling. But that means you've done it in PSUs that use forward topology?

[c_hegge]

Re: Power supply build quality pictorial. part 2

^
Yes. I've pulled 20A from 20A rectifiers on PSUs with forward topology without incident for as much as 15 mins at a time (I did try for more, but the OCP wouldn't allow it). In half bridge PSUs, I've been able to pull quite a bit more than the rating of the rectifier without incident.

Nearly all of the common ones common rectifiers (like the STPS3045CW, Probably the most common rectifier I find) are rated for 120*C or higher.

[Wester547]

Re: Power supply build quality pictorial. part 2

I have two more questions... does forward topology change how effectively the specs of a capacitor filter the transient voltages (and supply power) to any one rail/output (rather, does it change the formula for that?)? And, furthermore, is the amount of power any one rail can deliver (in amps, less than maintaining a clean voltage per output) determined by only the rectifiers or by the specs of the capacitors on that rail also?

[Pentium4]

Re: Power supply build quality pictorial. part 2

Kinda disappointed with this Antec, mostly because of the cap choice. Looks like an FSP build. At least it has APFC. And I paid $10 for it brand new. Hooray for voiding the warranty straight out of the box.

All output caps are CapXon there's 2 Teapo's. One on the 5VSB and that tiny one next to the MOSFET's. Bridge rectifier mounted to the heatsink is a GBU805. Going to recap the entire thing. Would you guys trust this for 500W with a recap? I was thinking more along the lines of 430W continuous. It is 80 plus at least. What do you guys think? Either way, great for $10

I recapped this entire PSU except for the primary cap. Replaced the 2200uf 16V Teapo on the 5VSB to a 3300uf 16V UCC KY cap. I replaced all the 1000uf 16V CapXon's with 1500uf 16V UCC KY's (and there were 7 of them) so I'm hoping the ripple will be in check with this thing

[goodpsusearch]

Re: Power supply build quality pictorial. part 2

So, you are saying that each of the 3 main outputs (3.3V, 5V and 12V) had only 2x1000uF output capacitors??

[Th3_uN1Qu3]

Re: Power supply build quality pictorial. part 2

Spire SP-600W Rocketeer VI. OEM is Topower. Jenpo caps everywhere, the owner swapped some of them but still wouldn't power up. Turned out to be a bad 3842 on 5vsb, haven't tested the main PSU yet as i've removed both heatsinks. Original caps were Jenpo, most of them bloated including the primaries, some just dried out and the PSU is almost new... Spire blew all their budget on those fancy cables.

It's half bridge, but it looks beefy enough to do 600W. Primary switchers are a pair of 2SC3320. Two SBL3040PT for the 5v rail (60A total), two YA868C15 for 12v (60A total), one SB2040PT (20A) and one P80NE03L (80A) for 3.3v. Obviously, the limit is given by the diode. Also found on the secondary heatsink is *gasp* a 7905! This thing has a -5v rail, which shows just how old the design is. It does have active PFC however, with a L6562N and two IRFP460A.

[goodpsusearch]

Re: Power supply build quality pictorial. part 2

Look: https://www.badcaps.net/forum/showthread.php?t=12484

They are similar. The Tagan had Panasonic primary caps, yet they failed dry. I think that this is due to the APFC add-on board or the heat (or both?)

[momaka]

Re: Power supply build quality pictorial. part 2

^ That TL494 and some of the resistors next to it seem to have gotten quite toasty. Not good! Otherwise the PSU looks nice.

[Behemot]

Re: Power supply build quality pictorial. part 2

...

Are the primaries really bulged under the plastic cover? It tends to seems so, but its just for safety, the actuall vent is under it.

[Wester547]

Re: Power supply build quality pictorial. part 2

This might sound silly but does anyone know why yellow tape is often wrapped around secondary and primary capacitors?

[Th3_uN1Qu3]

Re: Power supply build quality pictorial. part 2

Are the primaries really bulged under the plastic cover? It tends to seems so, but its just for safety, the actuall vent is under it.

First thing i did was rip it out and check - yes, they are bulged.

[c_hegge]

Re: Power supply build quality pictorial. part 2

Time to recap it and disable the PFC. I think in those PSUs, you can just un-solder the four wires coming from the add PCB, and solder a bridge rectifier in their place.

[Th3_uN1Qu3]

Re: Power supply build quality pictorial. part 2

I'm going to keep the PFC. As for the caps, going after them today.

[ben7]

Re: Power supply build quality pictorial. part 2

I'm going to keep the PFC. As for the caps, going after them today.

You should dissect them, I would like to see if there is discoloration/arcing inside those lame things!

[Th3_uN1Qu3]

Re: Power supply build quality pictorial. part 2

I will definitely dissect the primary caps as i can hear rattling inside. I'm sure they're smaller than the cans.

Btw, all up and running now. All that was wrong with the main supply was the caps. Pics tomorrow.