The joke about this power supply starts on the website from the original manufacturer. As you can see there, all their models are deliberately overspec’ed. For example, the “KY-550ATX” model is a “450 W” model, believe it or not. The problem, however, is that on the website from the original manufacturer there isn’t any power supply with the exact current specs as present on the label from this unit.
If you take the 500 W model sold by Apevia (ATX-AS500W-BL), you will see that it has the same label as the Young Year YP-600-AB model, which is labeled by Young Year as a 500 W unit. But on Apevia’s website there is one interesting thing. Two, as a matter of fact. The first one is that contrary to Young Year’s website all the currents are labeled as “maximum,” with lower specs labeled as “normal.” These “normal” currents would be 20 A for the +3.3 V output (instead of 28 A), 24 A for the +5 V output (instead of 30 A) and 25 A for the +12 V output (instead of 34 A). Even then we think these numbers aren’t real, as we shall discuss in more details in a moment. The second thing we notice was this funny typo, where “tolerance” was written “torrance.”
The model we bought was labeled by Brazilian distributor Leadership as a 550 W model, and the crazy thing about it is that is impossible to find any model at both the original manufacturer’s (Sun Pro) and Young Year’s websites that has the same label as this unit. Even worse, as you can see in Figure 14, the label also lists the specs for two other models, 600 W and 700 W, that we also can’t find at any website (original manufacturer and "clone" manufacturers). So we think Sun Pro will simply print whatever you pay them to print. Do you want a 900 W power supply? No problem, we will make the sticker for you!
As we saw in the previous page, the +3.3 V, +5 V and +12 V rectifiers used by this power supply can only deliver up to 30 A (99 W), 30 A (150 W) and 10 A (120 W), respectiv
ely. Keep in mind that these are the maximum currents and power specs for the rectifiers only, the maximum current/power the power supply is able to deliver will depend on the other components used, especially on the transformer, on the coils and even on the width of the printed circuit board traces.
The point is. NO YP-AB model can deliver what the manufacturer says. If you take the smallest model, YP-450-AB, which is officially a 350 W unit, its +12 V line is labeled as 15 A while the +12 V rectifier can only deliver 10 A!
The difference between the components used and the Leadership model we bought is outrageous, they labeled the +3.3 V, +5 V and +12 V outputs as capable of delivering 32 A, 34 A and 36 A, respectively, which is impossible using the components we found inside this unit. The most absurd difference is on the +12 V output (10 A/120 W vs. 36 A/432 W).
Some reader could point out that we are wrong as the maximum current of each rectifier is labeled under temperatures above 100° C and thus they could deliver a higher current when running at a lower temperature. This could make a little sense, however we’ve never seen a power supply where the rectifier maximum current is lower than the current printed on the label. Actually it is the contrary that normally happens: the rectifier maximum current is higher than the power supply labeled current – the double, in some cases.
The information that this is a 550 W (or any other power spec above 350 W) is a complete lie. Unfortunately we don’t have the required equipment to see the maximum power we could pull from this unit.
Just as an exercise, if we added up the maximum theoretical power for the three main positive voltages, we would have 369 W. Since +5 V and +3.3 V outputs are connected to the same transformer output, we cannot simply add these two powers, as one output limits the other. If we considered a combined power of 150 W (the maximum theoretical power for the +5 V output), we would have a maximum power of 270 W for the main positive voltages. Keep in mind that this is a theoretical value and the real value is usually lower.
Another detail is that this unit has a -5 V output, which is present only on very old power supplies, as this output was removed from power supplies years ago.