Markings on the WX-DC12003 Switching Power Supply

Thread Starter

nct73@

Joined Apr 19, 2024
5
If you look at the photo, you will see markings that point out the input (blue circle) and output (green circle) I assume the "L & N" on the input is for AC input, and the "+ & -" is for the DC input which the text on the one photo explains. But when one looks at the bottom of the PCB, There is "a & -" marking with "DC310V" (red circle). These two points are connection points for the onboard 4.7uf capacitor.

Does anyone know why these markings are on the PCB❓ Is this possibly a second DC voltage in point, or maybe a "test point" indication❓
 

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sagor

Joined Mar 10, 2019
914
That is probably the DC voltage at the filter capacitor after rectification of 220VAC. In other words, a general "estimate" of the voltage on that filter capacitor. Without seeing what is under that Cap, that is just a best guess (I assume there is a rectifier under the Cap).
Why they would label it is unknown, no reason to do so unless it is meant to be a warning that there may be a residual DC voltage of 310VDC after disconnecting power from the device. If input was 270VAC, then the cap would have about 380VDC on it. If powering from a 120VAC, the Cap would have about 170VDC on it.
 

Thread Starter

nct73@

Joined Apr 19, 2024
5
Good guess, nasaspook ❗ There is a MB10F-13 BRIDGE RECTIFIER (1PH 1KV 800MA) SMD rectifier under the capacitor. You can just make it out in the attached photo.
And your "guess" as to why they marked it is plausible. But why? There are no components mounted on the underside of the PCB, and the bottom of a PCB is usually not visible when it is "in position" in a device. So a "warning sign?" Also, if there is 310V at that point, there is 310V in a lot of other places on the PCB, although certainly not as easy to touch as the long leads of the capacitor on a corner of a board laying down as it is..

All-in-all, though, I think you got it right❗
 

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Thread Starter

nct73@

Joined Apr 19, 2024
5
It also indicates that you can feed a 300 V DC at that point instead of a AC input.
That is also what I sort of thought, and what motivated me to ask the question, However, one can also apply a DC voltage at the regular inputs (what you called an AC input) indicated by the + & - there.
 
"DC310V" That's the safety warning :p
Were you expecting more from this cheap piece of sh@!@ power supply. It's won the race to the bottom.
No fuse, no EMI filtering at all, dangerous PCB spacings and a transformer wound by villagers. Then there are the gutter grade electrolytic capacitors.
I would never use such junk in a project.
 

Thread Starter

nct73@

Joined Apr 19, 2024
5
"DC310V" That's the safety warning :p
Were you expecting more from this cheap piece of sh@!@ power supply. It's won the race to the bottom.
No fuse, no EMI filtering at all, dangerous PCB spacings and a transformer wound by villagers. Then there are the gutter grade electrolytic capacitors.
I would never use such junk in a project.
Some of us have more money than others❗
 
That PSU is $1.00 race to the bottom champion.
Do you think you could spend a little more for something that will not electrocute people or burn the house down? Something that has been tested i.e. hi-pot at least, has a fuse somewhere.
Look at the PCB spacings between HV DC and the secondary. People here skilled in the art will cringe at that. Never mind the other side of the PC board.
I have an issue with hobbyists and makers using super cheap mains SMPS from china that have blatant regulatory violations - for safety and EMC. I'm harsh because this thing is pretty terrible. Of course it fails emissions.

WX1_DC12003_pic.jpg
 

Thread Starter

nct73@

Joined Apr 19, 2024
5
That PSU is $1.00 race to the bottom champion.
Do you think you could spend a little more for something that will not electrocute people or burn the house down? Something that has been tested i.e. hi-pot at least, has a fuse somewhere.
Look at the PCB spacings between HV DC and the secondary. People here skilled in the art will cringe at that. Never mind the other side of the PC board.
I have an issue with hobbyists and makers using super cheap mains SMPS from china that have blatant regulatory violations - for safety and EMC. I'm harsh because this thing is pretty terrible. Of course it fails emissions.

View attachment 320513
I understand you completely, and the issues you bring up. As shown in the link you provided, there are probably ways to take care of some of these issues with external components. However, I am only working with 120V AC (USA), and needing very little power, maybe up to the 700ma limit.

My biggest issue is I like to do very small projects, and most "safer" supplies like those made by Meanwell are in the 2" size minimum, which is too large to include in my miniature projects.

Perhaps you have some suggestions?
 
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