Another Delux 500w psu

[mariushm]

Got this power supply as a "tip" for fixing a 19" lcd monitor a few days ago.

It was pulled out from a pc in an internet cafe location where people used to smoke, so it smells a bit and I had to clean it of nicotine and other gunk inside.

Owner said it doesn't work and he thought the main capacitors were faulty. One of them is indeed swollen but my feeling was that the glue was causing some problems, not the capacitors.

When I first got it, it wasn't starting up at all, no 5v standby, nothing.

So i opened it up, cleaned the backside with some cotton dabbed in isopropyl alcohol.
Main capacitors are asia-x, Desoldered them... they say 470uF on them, one tested 410uF 0.15 ohm esr, the slightly swollen one tested 390uF 0.2 ohm. While I had them off the board I also rubbed the area around the main capacitors. Soldered the main capacitors back on the board.
I also tested the main transistors and they seemed fine.

I tested the diode on the 5v standby and it measured 0.15v in both directions. I desoldered it, measured it out of circuit and it measured fine. Put it back in the circuit and it measured fine... puzzled by this... maybe i flexed the wire a bit and removed some short inside the diode? Was it a bad solder joint?

Anyway.. plugged the psu back in the mains and now I had 5v standby... shorted the green wire with a 1ohm resistor to ground and now power supply started right up, 12.15v, 5.1v, 3.35v, -11.3v.. only one not sure may be the -5v which may measure 5v but I may have probed a different wire by accident.

I'll replace the diode anyway, just to be sure but otherwise i don't know.. could it be something else, some cold joint, something that I now moved and made it work?

Here's pictures. 13009 primary transistors, bu375 for 5v standby (i think), 16a to-220 diode set for 12v, some 20-30a (probably) for 3.3v and 5v.. I can't tell from pictures the exact values and I dont want to touch the psu again because I'd have to wash my hands again.

[SM-Piyes90]

Re: Another Delux 500w psu

Maybe after removing and putting back those big capacitors things got alive again due to heat , just a guess .

[Escort Eagle]

Re: Another Delux 500w psu

What is your PSU current condition ? Is it running now ?? Every PSU does not have -5V . Is there any White Cable in your PSU . If you have any White cable in PSU, then you can get -5V, otherwise Not .

[mariushm]

Re: Another Delux 500w psu

You know, now that you mention it, I didn't even check the label. It doesn't advertise the -5v rail, I just assumed being such an old design it would have it.

The power supply ran on the workbench with the power good signal tied to ground. It's still open on the bench because I still plan to change that diode just to be sure. I may also switch around the rectifier diodes so that the 16A one will go on the 3.3v instead of 12v. Unfortunately at the moment I don't have beefier rectifier diodes in to-220 package right now.

[Escort Eagle]

Re: Another Delux 500w psu

Sorry, I do not understand what you are trying to say !!

[SM-Piyes90]

Re: Another Delux 500w psu

You know, now that you mention it, I didn't even check the label. It doesn't advertise the -5v rail, I just assumed being such an old design it would have it.

The power supply ran on the workbench with the power good signal tied to ground. It's still open on the bench because I still plan to change that diode just to be sure. I may also switch around the rectifier diodes so that the 16A one will go on the 3.3v instead of 12v. Unfortunately at the moment I don't have beefier rectifier diodes in to-220 package right now.

Why do you want to change the diode , instead i would change the two big caps .

[c_hegge]

Re: Another Delux 500w psu

^
Because the Diodes will have more of an effect on the efficiency

[mariushm]

Re: Another Delux 500w psu

That 16F020C part is a 16A 200v diode set ( 8A x 2):

This is also only valid at up to 100c - if the internal temperature goes above 100c then the diodes get derated so you have even less current. With those heatsinks it's possible to get close to 100c inside the component.

16A x 12v = 192 watts .. really little value on 12v for a 500w psu, especially considering modern computers use 12v a lot.

I would change the big capacitors but I don't have something matching that "in stock" and this type of psu is just too shitty to be worth paying about 3-5$ for some good capacitors. If (or better put when) I'm going to get some other faulty psus, I'll recycle some caps from those. At the moment, the ~ 400uF on each cap is enough.

later edit. If you mean why that diode by the 5v standby? Well, simply because it wasn't working before, and power supply started working after I resoldered it back to the board.
Just in case there's some fracture on the diode that made it short out (it was measuring 0.15v in both directions when faulty), or there's some issue with the diode itself, it's better to be safe than sorry and just replace it.Diodes are cheap, and I have a bunch of them in my boxes of spare parts.

[mariushm]

Re: Another Delux 500w psu

So I found a FR302 in the spare parts and replaced the dubious 1n5822. Both 3A, both fast diodes, should be fine for 5v Standby 2A max.

Took out the rectifier for the 3.3v and it turns out it's a 20A 45v max rated part, so I won't gain much, just 4 amps.


As you can see... the 500w rating on label is a dream ... 20a @ 3.3v , 20a @ 5v, 16a @ 12v.

Changed the main capacitors with a couple I found in the box of parts, I think they were from another Delux that was only rated for 400w. They say 330uF on the label but really they're only rated for 220uF.

So I'm going down from ~ 390uF per capacitor to 220uF per capacitor. It will decrease the maximum power it can output so I'm not very happy about it but really, this power supply won't see a system that uses more than 150 watts.



Secondary capacitors are all Nicon and KME, 1000uF 10v or 16v. I thought for a few minutes if I should replace them but in the end, it's not really worth using good capacitors on such a psu and the current ones look OK.

[momaka]

Re: Another Delux 500w psu

Took out the rectifier for the 3.3v and it turns out it's a 20A 45v max rated part, so I won't gain much, just 4 amps.

You won't gain anything if you even tried that, because that rectifier would have likely shorted on the 12V rail. Most half-bridge PSUs require the 12V rectifier to have at least a 60V rating (because the rectifier itself will be seeing 2 x 12V plus some more from inductive spikes). Also needs to be of the fast-recovery type. Schottky don't always have as fast of a recovery time as do fast rectifiers, so this tends to limit what you can put on the 12V rail output of a H-bridge PSU.

especially considering modern computers use 12v a lot.

They do. But if you have a modest system, it's enough. The most I've ran on a 16A rectifier in a H-bridge PSU was an AMD Athlon 64 FX-57 (a 105W TDP CPU) and a Radeon 9700 (pulls around 45W at full load mostly from 3.3/5V rails combined). Or an Athlon 64 3200+ and GeForce 9800GT setup might have been more power hungry, I don't know. But both ran well and PSU was nowhere near overloaded.