XP480 (400W)

This model doesn’t have a serial number or any marketing name since it ships only bundled with Thermaltake’s system cases (Tsunami Dream, Soprano, etc). However, I have a reason to place it in exactly this place of the review, before the TR2 XP550 (W0070) model. They are obviously much alike to each other in their internal design as well as in their model names. So, the XP480 can be viewed as a junior model in the low-end TR2 series (but speaking formally, it lacks “TR2” in its name and is not described in the corresponding section of the Thermaltake website).

This PSU has a simple gray case with two fans. Its actual manufacturer is HEC/Compucase.

The PSU offers the following cables and connectors:

• A mainboard power cable with a 20-pin ATX connector (36cm)
• A CPU power cable with a 4-pin connector (35cm)
• Three cables with 3 Molex connectors and one floppy mini-plug on each (36cm from the PSU case to the first connector and 10cm more to each next connector)
• One cable with 3 Molex connectors (36cm from the PSU case to the first connector and 10cm more to each next connector)
• A cable with one SATA power connector (35cm)

It’s roomy inside this power supply: the components are all of modest size, the heatsinks are simple bars with punched-out “fingers” on top. The assembly quality is high, however, just as you can expect from HEC, so I can’t have any complaints here. The circuit design is classic, with group voltage regulation and without PFC. The main regulator is based on a UC3843B chip; the output voltages supervisor is based on a HY510N chip. The marking on the PCB – a table that tells which fuses to use for units with different wattage – set me aback as I couldn’t find wattages higher than 300W in it. The PSU label has a somewhat different number in large letters, hasn’t it?

At about the same time as I was testing the XP480 I bought a cheap microATX system case Ascot 6KR2 for my home computer (this is an ordinary HEC/Compucase shipped under the Ascot brand for a Russian distributor). It came with a 200W HEC 250AR-TF power supply and I was greatly surprised to find that the circuit design and the components used in that PSU were an exact copy of the Thermaltake XP480! The only difference between the two was their cooling: the 250AR-TF is cooled with one fan while the XP480 with two fans. Well, the extra cooling may help the transformer and the choke coils in the XP480, but its transistors and diode packs won’t feel any difference. They had to make the heatsinks smaller in the XP480 in comparison with the 250AR-TF to put in the second fan.

So, what is the real wattage of the XP480?

The label promises a sustained output power of 400W and a peak load of as much as 500W, but the currents don’t reach the level of the standard 300W unit as described in the ATX12V 1.3 specification – it must have a load capacity of 18A on the +12V rail whereas this PSU offers one ampere less there. On the other hand, the typical 250W power supply of the ATX12V 1.3 standard has a +12V load capacity of 17A, i.e. exactly as in the XP480. That’s another meaningful coincidence after the circuit design being identical to the 250W HEC.

The cross-load diagram of this PSU looks well, except that the +5V voltage is a bit too high when there is a low load on this rail. It doesn’t go beyond the acceptable limits, though, deflecting by no more than 4% from the nominal value (a 5% deflection is considered acceptable). It’s only in the top right of the diagram – where the load power is 310-320W – that the power supply behaves in an odd way. Do you see those multicolored patterns?

After the building of the cross-load diagram, the next text in our PSU-related reviews is the measurement of the output voltage ripple. These measurements are in fact made as the final step in the test procedure because I measure the voltage ripple under the maximum load on the PSU. Before doing that I am increasing the load in steps of 50-100W and leave the PSU to heat up for 20-30 minutes under each load. After that I measure the power factor, efficiency, and fan speed (the heating up is actually necessary for the fan speed to become constant). And it’s only at the maximum load power that I attach our oscilloscope to the PSU’s output.

Alas, the XP480 just didn’t make it to that point. When the load exceeded 310W, the output voltages suddenly dropped by 10-20% (I took a final look at the multicolored patterns in the cross-load diagram just in this area) and the overload protection was triggered in the PSU at a load of 320W (I say, where is the promised peak of 500W?!) My further attempts to find a maximum load under which the PSU would be stable ended in a loud plop inside the PSU case and the power supply shut down. For ever. The autopsy showed that the switching transistor of the high-voltage inverter had actually exploded in two.

So, my apprehensions were well grounded and I think it’s a proven fact that the XP480 is a remarked 250W unit from HEC. Contrary to the impressive specification, the XP480 just cannot yield more than 300W of power. 250W is the maximum load the XP480 is sure to sustain for some long time, not for just five minutes. But let’s get back to the tests. Perhaps it will do as a 250W unit?

The PSU has two cooling fans; their speed is adjusted in an almost linear manner until about 250W. After that the fans work at their max speed. By the way, this is indirect evidence that the PSU was initially meant for a peak load of 250W.

The efficiency of this PSU isn’t high, being only 75% at the maximum and closer to 72% on average. This is higher than the standard demands (ATX12V 1.3 power supplies must have an efficiency of no less than 70% at full load), but isn’t impressive at all in comparison with modern models whose efficiency is closer to 80%.

The power factor is low at 0.68, but this is quite a typical number for a model without any kind of power factor correction.

I’d like to divide my impressions about this power supply in two parts. One part is concerned with the 250W unit from HEC and the other with the 400W label from Thermaltake.

As an inexpensive 250W power supply for office computers and even midrange home systems the XP480 looks quite good. It has the necessary connectors (even too many of Molex ones); its parameters are good and it is quiet (particularly, much quieter than the original HEC 250AR-TF equipped with one cooling fan). So, there is nothing to cavil at. It doesn’t look impressive against today’s monsters with twice the output power, but do you really need hundreds of watts if there is no top-end graphics card and high-consumption central processor in your computer? Not to run long for examples, I am now writing these words on a computer with an Athlon 64 3800+, a Radeon X800 XL graphics card, one gigabyte of system memory, one hard drive and one DVD-burner, and all this stuff works without problems in a barebone system case with a 250W power supply from Enhance with a maximum current of only 16A on the +12V rail. I guess this configuration is the home mainstream for today, let alone office machines that often lack even expansion cards because everything is integrated into the mainboard. The XP480 suits well exactly for such computers.

However, Thermaltake thought it necessary to stick a label on this power supply that declares an output power of 400W and even promising a peak output power of as much as 500W! But as I made sure in my tests, even 300W is too high a load for this power supply. Depending on the particular conditions, either its overload protection reacts, or the attached system hangs up due to a sudden drop of the output voltages, or the unit just burns down. And the XP480 comes in system cases that can hardly be called cheap: the retail price of a Tsunami Dream is about $140. This case is unlikely to be bought for a low-power office machine I guess.

For me, the problem is not even that the power supply isn’t up to the class of the system case it comes with, but that the customer is overtly lied to. The wattage specified on the PSU misleads the user as to how much power his/her system needs. Imagine a person that buys a Tsunami Dream and assembles a gaming system in it with two graphics cards and a top-end processor. He hears a plop on first turning the system on, opens the case, looks at the label that reads “400W” and comes to the conclusion that this is too low wattage for his computer! And this user then goes to buy something like a 680W unit, for example the not-very-cheap W0049. And this user will be lucky if he gets the second revision of this W0049 because otherwise he may find that 680W is not enough for his system, too! So now you see where those stories that a power supply of 700W and no less wattage is required for a gaming computer come from. And all these watts cost you money whereas a power supply with an “honest” 400 watts of output power would be more than enough.