Fsp raider ra 750

[Taruga]

My power supply (FSP RAIDER RA 750) suddenly died, powers on, fan spins and immediately powers off.

The 5vsb is ok.

Capacitors look good, but the first one I tested (the big one from Teapo) doesn't look so good.

[stj]

Re: Fsp raider ra 750

5.6nF - that cant be right.
try it with a multimeter - remember to discharge it with a screwdriver first.

[Taruga]

Re: Fsp raider ra 750

It's discharged, I've made sure of it.
I also tested with another tester I have and it gives the same result.
What should be the normal ESR value for a 420v 390uF capacitor ?
It's the first time I have issues with a big one like this, 18 Ω looks way too high. It should be below 1 Ω or something like that, right ?

Anyway, I´ve just ordered a couple of 390uf 420v Nichicon rated 105ºC, the Teapo is rated 85º C.
I can check capacitance and esr value when I get the new one...

[Taruga]

Re: Fsp raider ra 750

I've tested other capacitor I have here: 400v 150uF with the same tester, looks fine. Low ESR

[R_J]

Re: Fsp raider ra 750

Do you get any of the +12 or +5v when the main power supply turns on? If not, check the switching fets and secondary diodes for shorts, if it is a bad cap it is likely one of the small ones in the primary circuit gone open
It is very unlikely the main cap is bad and if it was weak the power supply would likely still work unloaded

[stj]

Re: Fsp raider ra 750

well the main cap could be blown open-circuit.
pretty rare though.

[Per Hansson]

Re: Fsp raider ra 750

5.6nF - that cant be right.
try it with a multimeter - remember to discharge it with a screwdriver first.

I find many dead primary side caps when the PSU has APFC.
As mentioned be sure to check for shorts, commonly the PFC diodes will short when the main cap goes bad like this.
The easiest test is a dim bulb tester (Google it or search for it here on the forum)

[Taruga]

Re: Fsp raider ra 750

Hi Per Hansson,
Thank your for your suggestions.

I don't have much experience with this things.
I just started repairing PSU's, I´ve successfully repaired 2 out of 3.
This is the 3rd one, and I´m waiting for the new capacitor.

About the dim bulb tester, is that used to light up the lamp in case of a short when powering or connecting the PSU ?
I have to build dim bulb tester, before I replace the big capacitor I'm waiting for.
That looks like a usefull tool.

I've connected this PSU to mains and tried to start it up but It only works for about half of a second, I see the fan spin and then it imediatelly stops.
If there was a short on the primary, wouldn't the electrical panel of the my house shut down ?

Bridge rectifier is OK, I see one isolated diode that is also OK, then I see in that dissipation plate a thing with 2 legs, that should be the PFC diode. It's also reads OK.
Maybe the only fault is only the big capacitor.

[Per Hansson]

Re: Fsp raider ra 750

From your tests it sounds like the PSU is not shorted.
It's still a good idea to use a dim light bulb tester.
It will light up the bulb if there is a short, limiting the current that goes to the PSU.

[momaka]

Re: Fsp raider ra 750

5.6nF - that cant be right.
try it with a multimeter - remember to discharge it with a screwdriver first.

Oh, it can!


Full thread here:
https://www.badcaps.net/forum/showth...hlight=enermax

And here is another thread of mine with a busted main cap:
https://www.badcaps.net/forum/showth...ht=thermaltake

There are more of these threads here on BCN by other people, but I'm too lazy to look them up right now. Will do if you think it'll help, though.

It is very unlikely the main cap is bad and if it was weak the power supply would likely still work unloaded

Not at all.
I see it more often than I'd like to on PSUs with APFC.
Seems to be more common with CM6800 PWM+APFC controllers, but I'm sure it's happened to PSUs with other controllers.

I find many dead primary side caps when the PSU has APFC.

Same here.
APFC puts a much more considerable deal of stress than a regular PSU with line-connected caps. And when the caps are a Taiwanese or Chinese brand, that doesn't help either.

The easiest test is a dim bulb tester (Google it or search for it here on the forum)

I find that many APFC PSUs don't like the dim bulb test. Might need several 60-100 Watt bulbs in parallel to keep the APFC happy. I typically use a 450W heating element for cases like that. And I still can't put much load on the PSU before the APFC decides the line has dropped too low and it won't work.