Why does this Antec squeal

[c_hegge]

I got an Anted SP-400 from work. It had bad caps (fuhjyyu) and would squeal when running. On all the other antecs I've re-capped, the squealing goes away after the re-cap. On this one, however, it persists, even after the re-cap. I have used the following caps:

1x 3300uF 16v Panny FC
1x 4700uF 6.3v Nichicon HE
1x 3300uF 6.3v Panny FJ
1x 2200uF 6.3v Panny FC
1x 1000uF 6.3v Ruby YXF
2x 1000uF 6.3v (for 5vsb) Chemi-con KZE

Does anyone know why the squeal persists with this PSU?

[c_hegge]

Re: Why does this Antec squeal

Oh, and I forgot to add, the pitch and volume of the squeal vary depending on the load.

[kc8adu]

Re: Why does this Antec squeal

look for a 22@50 on the same side as the +5stby.its along the edge behind the opto.

[c_hegge]

Re: Why does this Antec squeal

OK, I found it. What should I replace it with? My only options for Low ESR are Panny FM or Nichicon HE

[999999999]

Re: Why does this Antec squeal

Either of those caps should be ok.

Squealing is caused by a switching frequency that puts loose magnetics' windings into a resonant frequency. All it necessarily requires is the loose windings, though since it is a regulated circuit a change in load can cause it, increase or reduce, change pitch, etc. Failing capacitor can effectively seems like a change in load since it's using feedback in a loop the capacitor is in.

In other words, if all else fails you either locate and replace the squealing part or fix the coils in place better with a dip in lacquer, putting epoxy over them, etc. Not so easy to do the latter if it's a transformer already wrapped up. Some manufacturers used to put heatshrink tubing over them with a limited amount of success, and/or for only electrical insulation depending on who you ask.

[c_hegge]

Re: Why does this Antec squeal

I replaced that cap with Nichicon HE, and the squeal still persists. I'm using it now in a computer and it's REALLY annoying. What now?

Also, do you think that whatever is causing the squeal could cause worse damage to the PSU? or is it just an annoyance?

[c_hegge]

Re: Why does this Antec squeal

Hello? anyone?

[stj]

Re: Why does this Antec squeal

you should change all the electrolytics, not just the big ones.

if it still screams then there is a fix using anti-corona laquer, or epoxy resin.

[Toasty]

Re: Why does this Antec squeal

Does it use SMD components on the solder side? I had a cold joint on a SMD resistor cause that.

Can you localize the squeal with a paper towel roll used as a stethoscope?

[ss627]

Re: Why does this Antec squeal

Take the rubber eraser end of a pencil or any other suitable thing and press down on the coils to see if it stops the noise or changes pitch.

[stj]

Re: Why does this Antec squeal

Does it use SMD components on the solder side? I had a cold joint on a SMD resistor cause that.

Can you localize the squeal with a paper towel roll used as a stethoscope?

SP series is covered in smd, and if they are all like mine then the soldering is crap.
(and that's being insulting to crap!)

[c_hegge]

Re: Why does this Antec squeal

Take the rubber eraser end of a pencil or any other suitable thing and press down on the coils to see if it stops the noise or changes pitch.

I'm not going to plug it in with the cover off. I've been electrocuted one too many times doing that.

[Toasty]

Re: Why does this Antec squeal

Then pitch it in the trash. Most of these require some checking with the cover off and probing to repair. It don't get done by magic.

[c_hegge]

Re: Why does this Antec squeal

I'm not giving up just yet. I'll try stj's idea of replacing all of the small caps. If that doesn't fix it, then it goes in the bin.

[Khron]

Re: Why does this Antec squeal

I've persevered in trying to revive an SP-500P (with a bunch of burnt parts), and i've eventually succeeded, without getting shocked, as you might see in the thread i started a bit below I think i read in one of these threads about "1oz of prevention > 1lb of cure", so if you're just careful and don't rush things, you should be fine.

I insisted on reviving mine. Dad got it for free from my cousin, it's worth at least 50eu / 70us$, and i managed to source all the parts i needed. Plus, it's CWT-made Talk about "Value for money"

Also, you might find some useful tips in this thread .

Good luck with the repairs

[Pyr0Beast]

Re: Why does this Antec squeal

It would perhaps be good to check the input capacitors. Those 200/400V ones.

[c_hegge]

Re: Why does this Antec squeal

I'm also not willing to touch the primaries. They rarely fail and, since I'm not an electrician, it's illegal here.

[Wizard]

Re: Why does this Antec squeal

Illegal? Explain?

Cheers, Wizard

[stj]

Re: Why does this Antec squeal

i wouldnt worry,
from what i'v seen, licensed electrician's are more dangerous than mokey's

arent your reg's that house wiring (lighting circuits) should have all wire joints twisted, soldered (with a blowtorch) and taped-up?

[ss627]

Re: Why does this Antec squeal

I still think you should put a small load on the PSU and plug it in with the cover off and press down on coils etc with a non conductive stick to see if the noise pitch changes. There is absolutely nothing that can go wrong unless you have a seizure and start poking fingers inside or put a prolonged heavy load on the PSU with no fan. You wont be touching anything inside except with a nonconductive stick.