Power Supply Unit¶
| Specifications |
|---|
| Input Voltage: 115V and 230V AC (choose the correct voltage by setting a switch before turning on the printer!) |
| Output Voltage: 24V DC |
| Power Rating: 500W, 21A max. |
| Fuse: glass tube type, replaceable, located between the power plug and the power switch |
| Fan: 24V, 0.10A, 60x60x15mm, model "Cheng Liang CHA6024RL-15B" (?) |
| External MOSFET: drives the 24V DC of the bed's heating coil and the mainboard |
The printer comes with a 500W / 24V DC / 21A "CHENGLIANG" power supply unit which can take 110V and 230V AC as well. It is mounted to the underside of the printer.
The powerswitch and the plug are located at the left hand corner in the back at the side of the frame. There is also a fuse integrated in the powerswitch box which you can pull out and exchange if necessary.
Choose The Correct AC Voltage!
Before plugging in the powercord and switching on the printer, make sure that you set the little switch for choosing the voltage to the correct value! You can access it from the back of the printer and either set it to 110V or 230V - so make sure everything is set correctly first!
Warning: Turn Off And Unplug The Machine Before Accessing The Connectors
It must be said at this point that you shouldn't access the PSU's connectors.
However, if you have to do so, make sure that you switched it off AND that you have unplugged it!
Accessing The Connectors
- If you need to access the connectors, you have to take off the metal plate on the underside which covers the connectors by taking out three screws.
The following picture shows the connectors of the PSU with the three 115V/230V AC wires on the right side (L = brown, N = blue, earth = yellow/green) and the 24VDC on the left side (V+ = red and V- = black). Mind the additional black wire that is connected to "earth" of the 115/230V AC connector.
On the very left side you can see a green LED and right next to it a white potentiometer. With this potentiometer you can adjust the output voltage - so if you probe the voltage at the 24V DC connectors and you don't have 24V there, you can adjust the voltage to the correct value.
Warning: Don't Open The PSU - And IF So, Don't Touch Any Parts Inside
It must be said at this point that you shouldn't open the PSU.
However, if you have to do so, make sure to not touch any parts on the inside!
There are capacitors built in which can give you severe eletrical shocks even if the machine isn't plugged in or switched on as they store electricity!
Dismounting The PSU
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If you need to dismount the PSU because you want to e.g. change the cover or have to change the fan, you need to unscrew four screws at the top which hold it in place.
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Then you have to take off the metal plate on the underside which covers the connectors by taking out three screws.
The following picture shows the PCB of the PSU - the fan isn't plugged in, the belonging connector is the white two-pin connector in the upper left edge area of the board.
PSU Fan¶
The fan is a 60x60x15mm, 24V, 0.10A type ("Cheng Liang CHA6024RL-15B" ?).
MOD: Change The Cover Of The PSU Housing¶
Warning: Don't Open The PSU - And IF So, Don't Touch Any Parts Inside
It must be said at this point that you shouldn't open the PSU.
However, if you have to do so, make sure to not touch any parts on the inside!
There are capacitors built in which can give you severe eletrical shocks even if the machine isn't plugged in or switched on as they store electricity!
Dismounting The PSU
-
If you need to dismount the PSU because you want to e.g. change the cover or have to change the fan, you need to unscrew four screws at the top which hold it in place.
-
Then you have to take off the metal plate on the underside which covers the connectors by taking out three screws.
The fan of the PSU is pretty loud, so one of the first things one wants to change is probably to mount a different fan. The fan itself isn't actually that loud though, the noise is mostly created by the way the cover of the PSU housing inhibits the airflow.
I found a model for a different cover, which was actually made for using a different (bigger) fan. I remixed it and closed that cutout for using the stock fan instead.
For making sure that nothing will get through those bigger holes, I hot-glued a piece of mosquito net to it from the inside. Instead of drilling holes for the stock fan, I just used two of the existing holes and added some washers for making the screws clamp the fan to the cover.
You can find my version at Printables.com: Anycubic Kobra Go/Neo PSU Cover (Stock Fan!)
Don't be irritated by the fact that it's named "Kobra Go/Neo PSU Cover" - the PSU being used here is exactly the same as at the Kobra Go/Neo, so it just fits perfectly.
The following picture shows the stock cover plate and the 'custom' one (yes, they are the same size, it just doesn't look like that on the picture).
The effect of changing the cover was actually massive, the noise reduction is tremendous - even with the stock fan being used. Suddenly I was able to clearly hear the part cooling fan kicking in when printing, I could barely notice that one before.
I put a smartphone with an app for measuring the noise on the x-axis part of the baseframe, with the microphone facing the direction of the mounted PSU, then I turned on the printer (so that only the fan of the PSU was actually running). With the stock metal lid being installed it measured 66dB, with the modification it measured 49dB!
The following picture shows the PSU mounted again.
As this lid sticks out a few milimeters and the clearance is already pretty low with the stock setup, I raised the printer a bit by mounting slightly taller feet I had laying around. You can also print some risers which can be plugged onto the existing feet.
If you do so and you're using Klipper and resonance compensation (aka Input Shaping), keep in mind that the vibrational behaviour will change and you therefore should execute a new resonance measurement.
UPDATE:
Since most people apparently don't use the mosquito net and don't use additional washers to mount the fan, I made a new remix of the model where I added struts in the hexagon cutouts as well as two holes for mounting the stock fan.
This is the link of the new model: Kobra 2 series PSU cover/lid (for stock fan and/or Noctua 6025)
The following picture shows the different versions.
The following picture shows the new version mounted.
External MOSFET¶
The 24V DC of the mainboard as well as the heating coil of the bed aren't connected directly to the PSU. Instead, both are driven by an external MOSFET board located at the underside of the printer as shown in the following picture.
The PSU is connected to the green screw terminal "+ DC IN -" at the bottom right.
The bed's heating coil is connected to the green screw terminal "+ HOTBED -" at the bottom left.
The mainboard is connected to the "+ 24 OUT -" connector at the top right.
The signal for switching the MOSFET to heat up the bed is provided by the thin wires at the top left which are connected to the connector labeled as "CONTROL".
Attention: Mind the polarity!
MOD: How To Add A Step-Down Converter For Using 12V Fans¶
When you want to add components which need a different voltage than the 24VDC the PSU offers, you can do so by using a step-down converter (or a step-up converter if you need a higher voltage than 24VDC). Simply connect the IN of the converter to one of the free 24VDC connectors of the PSU, dial in the voltage you need and then connect the belonging part to the OUT of the converter.
The following picture shows a typical "LM2596S" type step-down converter which can be used.
However, when you want to use e.g. 12V fans which speeds are usually controlled by PWM of the mainboard, you have to connect them differently. The following drawing shows how to proceed in that case, so that the PWM will still work.
Warning
The following circuit diagram about how to connect a step-down converter wasn't tested by me yet. It's assumed that the mainboard controls the PWM of the fans by switching the belonging GND of the connector.
Add An Additional Fuse
It is highly recommended to add a suitable fuse to the 24V line, right after the connector of the PSU. If your additional parts like the converter will fail, the fuse will melt - which can save you from burning down your house.
MOD: Add Additional Fuses To The 24V DC Wiring¶
It is highly recommended to add a fuse or a fusebox to each of the 24V lines. Pay attention to choose the correct 'size' of the fuse for the belonging part (ampere rating).
Doing so can save you from burning down your house if components fail or if the wires somehow overheat and start to burn due to broken strands (which causes a higher resistance) or a shortcut.
(..need to add pic..)