Need help repair dead AVF brand power supply

[ChaosLegionnaire]

Re: Need help repair dead AVF brand power supply

As for the input electrolytic caps: 2x 330 uF will limit you to about 200 Watts, 2x 470 uF to about 250 Watts, 2x 680 uF to 300-350 Watts, and 2x 820 uF and above for 400+ Watts.

does that statement only apply specifically to that psu design or to all psus in general? cuz i have an enermax liberty 500w and fsp amacrox 500w and both have one 330uF 400v primaries. and i dont think those "branded" psus were bullsheeting on the power ratings...

[Wester547]

Re: Need help repair dead AVF brand power supply

does that statement only apply specifically to that psu design or to all psus in general? cuz i have an enermax liberty 500w and fsp amacrox 500w and both have one 330uF 400v primaries. and i dont think those "branded" psus were bullsheeting on the power ratings...

Primaries in APFC PSUs store far more energy than primaries in non-APFC PSUs, because there's roughly ~385V going across an APFC primary compared to the ~170V going across the primaries in the voltage doubler.

[momaka]

Re: Need help repair dead AVF brand power supply

does that statement only apply specifically to that psu design or to all psus in general? cuz i have an enermax liberty 500w and fsp amacrox 500w and both have one 330uF 400v primaries.

Yes, that applies to all switchmode PSUs.

However, perhaps I should have been more specific. Note that in my above statement, I listed the capacity as 2x ### uF. But I forgot to say that this is when you have two 200V caps in series - which is often the case with cheaper, older, and usually non-APFC PSUs (there are some APFC PSUs that have 2x 200V caps in series instead of a single 400V or 450V, but it is rare).

When you have two equal capacitors in series, the total capacitance becomes half, but they can handle two times the voltage of each cap's rating. Thus, 2x 200V 330 uF caps in series will have 165 uF total capacitance and will be able to handle up to 400V DC.

With your Enermax and FSP PSUs, they already have 400V/450V caps, so the capacity you see is the actual capacity. A single 330uF 400v primary cap will be able to store approximately the same power as 2x 680 uF 200V caps in series.

Hope that clears it up a little now.