Zalman ZM600-LX – dual forward power supply

Conclusion and evaluation

The Zalman ZM600-LX managed to provide its rated power, but failed to deliver the power within the ATX specification. So in accordance with my evaluation methodology, it does not deserve its evaluation. Honestly, as this unit is a former mainstream model, it does perform much better than many of the low-end gutless wonders we have seen so far. There is nothing really dangerous about it for your safety or the safety of your components. But it still does not perform good enough to pass on ATX spec regulation. For the record, this is the 6th out of 6 different Zalman units which failed to deliver their power in accordance with ATX specification.

The voltage regulation is OK under combined load, but crossloading the +5 V rail gets us into some troubles. The ripple suppression on this and especially the stand-by rail under full load sucks. The hold-up time is at least above 10 ms, but still does not reach the ATX minimum. The good thing is that the OCPs are actually present and working, the bad thing is they are quite strict. And with the bad shunt soldering the unit was shutting down with just about 45 A applied on a +12 V load. But with the voltage on that rail at that very moment, it did not actually even provide the rated power output of that rail.

The soldering also needs a few boards. While at first glance it looked so-so, there were some suspicious solder joints. One of them being under the current shunt which has up to 45 A running through it is a real concern. I think an incorrect temperature in the solder bath combined with a poor cooling-down strategy was employed during its manufacture, but most likely those two things are not the only problems. The ZM600-LX is better than way too many other low-end units, yes. But please do keep in mind Zalman was flaunting this as their mainstream model not too long ago. Zalman still has a lot of work to do!

The ZM600-LX runs from warm to hot depending on the load and cooling. I have some serious concerns as to whether the unit actually delivers the promised efficiency. And this is also the main reason why it runs so hot. At the same time, it runs with noise ranging from audible to extremely loud. Zalman has been pushing their prices down very hard in the last few years so the price is nice. But for that money you only get garbage capacitors and a 2-year warranty which makes for a very bad combination with all that heat. It is possible that for builds with very low power demands, the 400W version may be OK with the waste heat. It could also actually keep the regulation and ripple suppression in spec because of the low power. But that’s the only case in which I would dare to use this model. Not that I am suggesting it for any use at all.

Pros	+ cheap + working OCP + PWM IC with integrated FET for stand-by + reasonable efficiency
Cons	− may not deliver rated +12 V output − poor component quality − bad soldering − very loud at higher load − runs very hot at higher load − bad voltage regulation and ripple suppression
Be aware of…	/?\ soldering quality issues /?\ buying this unit

Bonus

As I already had the ZM600-LX open a second time to fix the soldering on the current shunt, I took the time and re-capped the unit. The input capacitor has been upgraded to 390 μF/420 V (originally from the Be Quiet! Straight Power 10 700 W CM), and the output capacitors to a mix of Samxon RS and Chemi-Con KYB/KZN. Besides one small incident with reversing the −12V cap polarity the result was nice. I have not measured the hold-up time after the re-cap, but my estimate is that it now handles at least 15 ms.

The +5 V SB rail ripple has decreased significantly. It is still not ideal as it often reaches slightly over 50 mV, but it is now way better. Now I am confident this unit is OK to use, albeit with a strong recommendation of keeping the output below 550 watts.

Thanks

I thank the impakt company for providing the Zalman ZM600-LX.

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