Review: bequiet! 300W TFX Power Supply Unit BN136 Upgrade for Dell Studio 540s

Review: bequiet! 300W TFX Power Supply Unit BN136 Upgrade for Dell Studio 540s


The be quiet 300W TFX BN136 power supply unit fits nicely in a Dell Studio 540s and has ample power on it’s dual 12V rails to power an ASUS 1GB GeForce GT430 PCI graphics card with ease. It was not found wanting under the FurMark 15 minute stress test; one of the toughest tests for a power supply and graphics card to endure.

The power supply itself is a beautiful item and oozes quality with it’s enamel-black finish and it’s braided-quality cables.

The bequiet! 300W TFX BN136 power supply unit is packaged with a euro-type electrical cable, so you will have to consider an adapter or alternative cabling if your live in the UK.

It has only two SATA electrical connectors – daisy-chained together – intended for connecting a pair of drives stacked together. You will need more than this. A Molex to SATA connector needs to be factored in with your purchase.

The bequiet! 300W TFX BN136 power supply does not break any records in terms of operating quietly. It’s noise levels are slightly louder than those from the Dell’s original power supply unit. I would say it’s acceptable for general use but my machine is a dedicated Home Theatre PC, where quiet operation is essential. It’s certainly the noisiest item in my machine. Ironically then, it lives up to it’s name:

Shsh! Be Quiet!


Last year I purchased an EZCool 400W TFX Power Supply Unit as part of an upgrade I was doing to my Dell Studio 540s to replace its original Liteon 250W psu. I needed a more powerful supply to fuel an ASUS 1GB GeForce GT430 PCI graphics card I was installing as part of that upgrade. The new graphics card required a maximum of 18A on the 12V rail. The Liteon fell short of that but the beefier EZCool could deliver that with ease.

I disliked the EZCool 400W TFX psu because of the noise it produced. It was absolutely no good for use inside a media centre. Noise levels were too high. See my Amazon review here: EZCool 400W TFX PSU Review: Tim Wolverson

Recently, the EZCool 400W TFX psu died a smelly, electrical death and I was forced to start looking for a replacement. What I found was that the range of TFX power supply units was still very limited in the UK, particularly if you want one with an output greater 300W. Yes, it’s possible to ship good quality ones in from the States but the hefty shipping charges were too lofty for me; almost as much as the items themselves. So I started looking deeper into the subject of power supply units by seeking help on a number of forums. I certainly didn’t want to buy another EZCool 400W TFX psu. I’d had a guts-full of those.

I eventually started gravitating towards the bequiet! 300W TFX BN136 power supply unit as a favourite contender. bequiet! 300W TFX BN136 PSU

German engineering; energy efficient; boasting whisper-quiet performance; quality components; made to last with superior reliability. A best seller. And the more I began to understand the internals of modern power supply units, the more this item appealed to me, despite its lowly 300W output tag. I had discovered that a power supply’s output wattage was not the crucial factor in power supply selection. The total continuous current on the 12V rail(s) is the most important.

The manufacturer’s website offers an array of technical data on this unit. In terms of output, success or failure for me depended on one key attribute, the available current on the 12V rail to ensure a consistent supply of power to the graphics card’s GPU; 18A at 12V = 216W.

The bequiet 300W TFX BN136 psu has dual 12V rails and the maximum current of each rail is listed as:-

12V (1) – 14A
12V (2) – 16A

At first glance, the maximum current on each rail may lead you to conclude that neither rail can supply the 18A required for the ASUS 1GB GeForce GT430 PCI graphics card, or the sum of the currents totals 30A, meaning that there’s plenty of combined power on tap with some to spare. Neither assertion is correct.

If you look down the list of technical output data on the manufacturer’s website, you will find a rating:-

Max. Combined power 12V  =  250W

This means that the combined maximum current is 250W divided by 12V = 20.8A

So I know that this unit is capable of delivering the power required to my graphics card.

So why have dual rails instead of a single one? The simple answer is safety. Having too much current available on one rail could result in fire if there was an electrical short. There is also a risk of electrocution with high currents, even if the voltage is relatively low. It’s much safer to split the power and transmit it through more than one rail (pair of wires). Some power supplies with greater wattage have multiple 12V rails to keep everything safe. More details can be found in the relevant forums.

After checking other important technical data, like physical size, I ordered the bequiet! 300W TFX BN136 psu from Amazon.

Review: bequiet! 300W TFX Power Supply Unit BN136 in a Dell Studio 540s

1.     Packaging & What You Get in the Box.

The bequiet! 300W TFX power supply unit BN136 is supplied vacuum packed in a swish, black, cardboard box. The box boasts the unit’s features on the front, its technical details on the back and its awards won on the top.

The box lid was security-sealed, which I like very much. A good start.

The first thing I saw on opening the box was a euro-plug power lead for the power supply. I live in the UK, Amazon! It’s no good to me without an adapter! So that was a negative for me. Not a big one because I knew I could use the power lead I already had. But what if this were not purchased as a replacement or upgrade? What if it were purchased to build my own computer from scratch? Yes, I’d have to bear the cost and more importantly, the inconvenience of having to buy a compatible power lead.

The very least Amazon could do here, is throw in an adapter so everything can work straight out of the box or make it clear that this is what to expect.

The power supply is wrapped in bubble-wrap and the electrical cables are fastened together with an elastic band. There is a multi-language manual and a small bag of cable ties and black screws to secure the power supply in your machine should you be building a PC from nothing. A very well packaged item, with little chance of the unit getting scratched during transit.

With the psu free of its sheathing, you begin to feel what an excellent piece of kit this is. The weight of the unit suggests quality; the enameled black coating of the unit looks great; the quality of the braided cables is second to none. From every angle, the bequiet! 300W TFX power supply unit BN136 oozes quality and aesthetics.

2.       Fitting the bequiet! 300W TFC Power Supply Unit in a Dell Studio 540s

After the failure of my EZCool 400W TFX power supply, I replaced it with the original Liteon 250W power supply that came with my machine; just to keep the media centre alive until the bequiet! 300W TFX BN136 psu arrived. It worked to a fashion. It was adequate in enabling the continuation of recordings. Its under-powered output though manifested itself in occasional bouts of severe ‘stalling’ when watching even standard definition video; sound and video stutter, lasting for seconds.

I was certainly eager to swap power supplies the moment the bequiet! 300W TFX BN136 psu arrived.

I removed the Dell’s original power supply by removing the case lid; the fastening screws at the rear of the unit and all the electrical connections to the motherboard and internal hardware.

The bequiet! 300W TFX power supply unit BN136 slides back onto, and engages with the Dell’s case-lug nicely to secure the unit at one end. I used three of the supplied black screws to secure the power supply to the chassis of the Dell 540s. The screw holes aligned perfectly and the unit was fixed solidly with the screws tightened.

I then proceeded to connect up the power cables. The CPU power cable was long enough to reach the connection point on the Dell 540s motherboard. There was enough length to route the cable around motherboard heat sinks and the graphics card to make a neat job of it. I had read reviews elsewhere that this cable was not long enough in some cases. All I can say is that it was of ample length to fit in the Dell 540s. As a comparison, it was equally as long as the CPU power cable of the original Dell psu.

I then proceeded to connect main power to the motherboard. The bequiet! 300W TFX psu BN136 is equipped with 20-pin and 4-pin motherboard connectors that can be combined to make the 24-pin connection for the Dell 540s. I had to remove the front fascia of the PC and push the DVD ROM forward to gain access to the motherboard connector.

Connection then was simple. I slid the DVD ROM back into place. Conveniently, the braided part of the motherboard cable terminates some distance before the plug. This makes it easier to fold the wires flat underneath the DVD ROM where there isn’t much space.

More than likely, you will need to purchase a molex to Sata power adapter to increase the number of available Sata power connectors to four.

The bequiet! 300W TFX power supply has only two Sata power connectors daisy-chained on the same braided cable. In the Dell 540s, the HDD is mounted some distance away from the DVD ROM, and at right angles. This cable alone then is not physically capable of supplying power to both devices. I used this cable to connect up my SSD & HDD which are situated one on top of the other. The distance between connectors was ample.

I used the molex to Sata adaptor to supply power to my DVD ROM.

I tucked the braided cable into the integral cable tidy inside the Dell’s chassis and boxed the machine back up.

3.      Conclusion

The bequiet! 300W TFX psu is not as quiet as it’s name would suggest. I’ve been listening to it’s fan noise over the course of a week now. I would say that it is a fraction louder than the original Dell psu. Not by much, but I’m disappointed that it is not any quieter. It’s in a Home Theatre PC after all and that’s what it is being judged on. It will do. But only just.

There a four fans in my Dell 540s. This is the loudest thing in there by far. And it runs continuously. By contrast, the case fan, CPU fan and graphics card fan are all whisper-quiet.

Seemingly, there is ample power for the ASUS 1GB GeForce GT430 PCI graphics card, a Blu-Ray ROM drive, HDD, SSD, dual core processors and a dual TV tuner card. The graphics card plays High Definition video content flawlessly.

I ran the 15 minute FurMark GPU stress test, keeping a close-eye on GPU temperature.
The test was successful in that the GPU on my card did not burn out and there were no stability problems caused by a lack of unsustainable power.

In Hindsight

I strongly believe that I should have expanded my choice of power supplies by purchasing a regular sized PC case; swapping everything over and seeking out a normal factor, uber-quiet power supply.

If the bequiet! 300W TFX psu had been a little quieter than the original Dell psu, I would have been very happy with its purchase, since it satisfied the power requirements of my hardware.

My Scores

  • Product Quality: 5/5 (A very well made unit; excellent quality braided cables)
  • Value for Money: 4/5 (Had to purchase molex to SATA power connector. Came with euro-plug)
  • Performance: 3/5 (Too noisey for my liking and marked down because of it’s misleading name)


Thanks for all the help at the jonnyguru.com forums.
My thread on those forums: Candidate TFX PSU for Dell 540s and Asus GT430
My concise review on Amazon UK

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