Sh 250 psu

[bigbeark]

This seems to be a well-built PSU dating to 1999.

One primary cap 330uf 200V seems to have oozed a bit.

The label does not specify max power on 3.3 and 5v.

Can I replace the 330s with 470 or larger caps, and will it have any benefits? The 2200uf 16v Capxon cap is a 10mm but the silkscreen has 12.5mm outline. The larger replacement cap would be closer to the coil. I this a problem? Is the power output limited by the Transformer? Please see pictures attached.

Thanks, Barry

[ben7]

Re: Sh 250 psu

That actually looks pretty darn good!

As long as the switchers and the output rectifiers are good enough, it should do 250w.

I would opt for two 470uF primary capacitors instead of 330uF.

As long as you use good quality (and correct rating) caps, being closer to the filter choke shouldn't make a big change.

[goodpsusearch]

Re: Sh 250 psu

Yep, just replace the primaries with 470uF and please tell us the primary switchers and the secondary rectifiers.

[tom66]

Re: Sh 250 psu

I don't call anything with CapXon in it good...

[ben7]

Re: Sh 250 psu

I don't call anything with CapXon in it good...

LOL, you misunderstood me - I meant that after a recap, it would be good.

Also, it has decent transformers, and a bridge rectifier.

[momaka]

Re: Sh 250 psu

The heat sinks are a bit small, but everything else seems good. Transformer is an ERL 35 - that's plenty for a 250W PSU if the rest of it was designed well. Once recapped, it would be a decent PSU for an older 5V -based computer (i.e. Pentium II, Pentium 3, most of AMD socket A platforms and older). Maybe add a few holes in the case for better ventilation too. It's not necessary, but I always do that since it greatly improves the cooling.

I too would encourage you to go with 470uF caps for the primary side. And get rid of all of the CapXon caps (well, as many as you can, anyways... the small ones can stay... see exception below). For that 10 mm 16V 2200uF CapXon - yes, get it replaced with a 12.5 mm cap. It will be much easier to find a proper replacement that way. The coil near it doesn't matter.

Exception for leaving small caps: replace all of the small caps connected to the 5VSB circuit since this PSU likely uses 2-transistor design. Specifically, there will likely be a 10 uF, 22 uF, or 47 uF cap rated for 25V or 50V on the primary side close to one of the smaller transformers - make sure to replace it if there is one. On 2-transistor 5VSB circuits, that's cap is critical for the 5VSB regulation.

[bigbeark]

Re: Sh 250 psu

Thanks everyone for your input. Thanks Momaka for your detailed info.

As requested these are the markings on some of the other components:

The Primary 3-legged transistor(?) is a PBL405

The mosfets on the back of the primary heatsink are TOP222Y

The large mosfets on the secondary heatsink are two S15D40C with one smaller S16C40C in the middle.

Most of the non-Capxon caps are HEC, perhaps they made this PSU.

I will replace the 330s with 470s and all the other caps with PW or FC.

I'll probably use this for one of my socket 462 motherboards.