Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

[Agent24]

My older machine in the lounge started having problems recently, and I decided to check out the PSU first, since I knew it had Su'scon capacitors and was a few years old.

Annoyingly (because I think now it's the motherboard on the way out) all the capacitors test fine for ESR, but I want to recap anyway, since I got them out.

Just one problem... while removing some of that crap glue from the PSU, I managed to rip the legs off one of the optoisolators. It's a NEC PS2561 with W suffix which denotes a CTR (current transfer ratio) of between 130 and 260% - and which has a Vceo of 80v.

The PS2561 is not available in NZ nor can I find a decent substitute.
Can anyone help? Do I *need* one with a Vceo of 80v? (most I see are 70v)

[budm]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

Can you trace out to see what kind of Voltage it is being exposed to or how it is being used in the circuit? 70V is more likely to be OK.

[Agent24]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

It's either the main feedback or the opto which takes the startup signal from the motherboard. I haven't checked which one, I think it's main feedback, have to desolder the PWM controller (on a separate board) to check properly

[everell]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

Here is you a handy cross reference guide.

[Agent24]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

Thanks but none of them match up 100% - all have lower voltage tolerance or lower current rating - and I don't know how much the difference may matter in this PSU. Probably it won't matter at all, but I don't really want to see the thing self-destruct.

[Agent24]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

Bought a "pulled" one from an eBay seller in France, but the markings are nowhere near as nice as the original which makes me suspect it's just another Chinese clone one. Yeah it might work fine, but ugh...

I'll trace out the circuit and find out exactly what mine was doing, hopefully you can help me work out if another part will work. Rather have a genuine substitute than an unknown.

[Khron]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

Now, in my admittedly limited experience, those optocouplers should have no reason to be subjected to more than... oh, say 20v (although in practice it would most definitely be lower than that).

Add to that the fact that, let's face it, a designer would have to be (bordering on) insane, to run just about any component on the bleeding edge of its ratings. I've cracked open a LOT of power supplies (ATX's plus an assortment of plugpacks and printer PSU's and whatnot) - more often than not, the optocouplers are either PS2561's (or clones thereof), or PC817's (same "disclaimer").

https://cdn.badcaps-static.com/pdfs/...b40670876d.pdf

Match up the variant with the similar CTR range as the original '2561, and you should be on your way

But, as always, i'm open to corrections in case i'm talking sh*beep*t

[Agent24]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

You are right. A designer would have to be insane to run the thing near maximum ratings. But some people do it anyway.

[kasfamily]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

Broken legs in PS2561 easily restore removing part of the housing and solder wire leads.Here as an example

[everell]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

What type of solder are you using to replace such tiny broken legs?

[stj]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

any fine solder will work, but lead-free is best because you need the strength.
it's more about the size of the iron tip

[kasfamily]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

This

[Agent24]

Re: Substituting NEC PS2561 optoisolator for Corsair CMPSU-400CX

I had a similar idea but figured it would be better to get a new one. Not only is the lead broken off, the case is cracked and I don't know if it still works properly anyway.

I think I'll figure out which one is for feedback and which is for PS_ON, use the good one for feedback and the clone one or the closest equivalent I can find for the PS_ON signal. That way if it fails nothing really bad should happen.