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Zalman ZM850-HP (850W)

Famous for its cooling solutions, Zalman has been producing power supplies for a few years already, but we don’t review them often. That’s because Zalman doesn’t try to fill the market full with numerous versions of its power supplies. The company offers few models, yet none of them has ever got a negative report from us.

The ZM850-HP is interesting for the breakup for the long-time collaboration between Zalman and FSP Group. Judging by the appearance and internal design, this PSU seems to be manufactured by Enhance Electronics. I don’t say it for sure because the actual manufacturer is not indicated anywhere. The UL certificate number on the label belongs to Zalman and there are no marks on the power supply’s PCB.

The PSU comes in a large black cardboard box which contains two smaller packages: a cardboard box with a PSU and a set of detachable cables.

The ZM850-HP is the only PSU in this review to be much larger than a standard ATX power supply. It is as long as 210mm. On the other hand, it has a higher wattage rating than the models described above.

The PSU features a dual-transformer design. To remind you, this design doesn’t itself provide some special wattage or stability. It only allows to replace one large transformer with two smaller ones, which often simplifies the overall component layout of the PSU. But the main feature that distinguishes the ZM850-HP from its opponents is the cooling system with heat pipes and heatsink at the back panel.

The concept of the cooling system is clear from the photos above: both heatsinks (with the power transistors of the main regulator and PFC on the left, and with output diode packs on the right) do not have any ribbing at all. Their heat is transferred to the third heatsink, made up of thin plates and located near the external vent grid of the PSU. From a theoretical standpoint, this cooling solution has both pros and cons – you’ll see how good the ZM850-HP is in practice shortly.

The PSU is cooled with a Zalman ZF1425ATF fan (140x140x25mm).

Having a total wattage of 850W, the PSU can yield up to 720W across its +12V rail which is split into six virtual output lines. The text to the right of the allowable load table specifies which connectors belong to which 12V line.

Besides eight connectors for detachable cables, the rear panel has a switch marked as Standby Noise Suppressor. The manufacturer doesn’t tell what this switch exactly does, so I had to find it out by myself. It was easy: in the On position, the switch sends a 20Ohm load to the output of the +5V standby source. Without any load the PSU emits an irritating rattling sound due to an obvious reason: switching power supplies work poorly without a load. So if your mainboard produces a sufficient load on the standby source and your PC doesn’t make any undesired sounds, you can leave the switch in the Off position. But if the PC begins to buzz quietly when you shut it down, you can set the switch to the On position to get rid of that sound. Note that the PSU’s power consumption in standby mode will increase by 1.25W after your doing so.

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