Which fan should I replace the fan in the power supply with?

The real question should be:

Should I change the fan in my power supply at all?

Many wish for a quieter power supply in their Anycubic printer. If you look for alternatives on Thingiverse, you will quickly find various mods that allow you to install a 92 or even 120mm fan through a printed cover full of honeycombs, which can then rotate more slowly and is therefore quieter.

But does that make sense?

By definition, there is no "high voltage" in the primary part of the power pack, but there is a very high voltage of 230 volts. Although this is quickly rectified, it is then inverted into a much higher frequency.

This is also the big problem: DC voltages of up to 120 volts are not life-threatening, but can cause burns. Alternating current, on the other hand, is deadly from 60 volts when it flows through the heart.

For this reason, all components, apart from the connection terminals, are inside a grounded metal housing.

Now let's imagine someone tinkering with a plastic housing. As a result, there is no longer a protective conductor. A simple wire from the fan goes through the honeycomb to one of the transformer poles on the primary side, or just to the supply terminals. Then there are 230V against ground at phase. If you then touch the printer or fiddle with the mainboard, that's it. The human being is grounded and the heart now adapts to the mains frequency of 50Hz.

A heart that is suddenly supposed to beat at 50 beats per second will probably no longer be able to supply the body with oxygen via the blood. Muscles that cramp due to the high tension will not let go. The FI (residual current device) does not trigger in this case!.

But something else funny can happen: You put a few cables through the housing a bit stupidly. Several kilohertz(!) of said AC voltage are present at the transformer on the primary side. If you misplace your cable, these can also be induced directly into another line. High-frequency magnetic fields get along quite well with small coils. Especially when the secondary coil has fewer turns. Then the tension rises even further.

This is entirely hypothetical and even I don't think it's easy to pull off, but in theory you can even roast yourself over a distance if you're dumb enough.

And then I see YouTube videos in which some people screw power supply units completely inexperienced, swap metal for plastic, fast fans with throughput through SuperSilent PC fans that only stir the air and then claim that they are "professionally modding" here. bullshit You build a life-threatening error source in your printer.

And hey, you modify a 15 euro power supply with a 20 euro fan instead of buying a brand name power supply from Meanwell LRS-350 for 45 Dollars, which has a temperature controlled fan and is quiet anyway?

I can not believe it.

And I'm sticking to it: Stay away from power supplies if you don't know exactly what you're doing. And when you do a "modding" like that, it shows that you don't know what you're doing.

So what should a power supply look like?

The normal counter-clocked switching power supplies, as they are installed in the PC, have a housing that is as closed as possible and only small air inlets in a few places. This ensures that:

1. as much as possible is covered by metal so that it is electromagnetically shielded and protected against unauthorized access (cables/fingers). It is also heat-resistant and can divert any hotspots from passively cooled components to the housing, because metal naturally conducts heat better than air or plastic.

2. The fan pulls the warm air out of the PSU. Totally intended to allow fresh air to flow in through the small openings. There are also components on the underside of the PCB that need to be cooled. Not only the large FETs at the output, but also all other components, such as input diodes, capacitors on the secondary part, PWM controllers, etc. All of this has to be cooled.

So to the question of what an ideal housing looks like:

• Metal on all 4 sides
• No openings to put fingers through
• Fan for suction

So the way you buy it. It all makes sense.

Is there a cheaper alternative?

My recommendation, if you absolutely want to keep the old power supply: Purchase a new fan that has similar airflow to the original but is less noisy. A clear purchase recommendation are the MagLev fans from Sunon, as they are cheap and also extremely durable. This Sunon MagLev HA60151V4 can be replaced 1 to 1 and is a whole lot quieter than the old vibration artist in the cheap Anycubic power supply.

As far as I'm concerned, you can do whatever you want. But please stop recommending such a mod to other newbies.

Thank you.