Junk I bought: My PSU won’t fix it

I have an Acer monitor that I’ve owned for about 15 years, and thanks to the extra money for a DVI socket sporting model for HDMI compatibility it still finds a place as one of my desktop monitors. It has a power brick that supplies it with 1 2V at 4.5 A and over the years it has made an annoying noise. Something magnetic is loose, and I really should replace it. So I went to AliExpress, and placed an order for a 12 V, 5 A power brick.

It’s a heavyweight

PS Marked as a PSU brick, 12V 5A
So far so good.

These units are quite standard, a box about 130mm by 60mm with an IEC socket at one end and a trailing cable at the other end for low voltage. I had enough of them in my hand over the years to know what to expect, so I was disappointed to find that when I got my PSU it was suspiciously light. 86 grams compared to what I expected about 250 grams, so I started to get a rat smell. Enter the world of a disconnected, and small switch-mode main power supply.

Access to Fort Knox should be easier than opening a main power supply in general, as they are ultrasonically welded together for safety. The few times I’ve done this required some dremal time and some swearing, so when this case turned out to be fairly easy to open with a screwdriver, it was clear that it wasn’t a high-quality item. Certainly my suspicions were confirmed, because there was a much smaller board inside. It is clear that this is not a 5 A power supply, so what There is I accepted?

For a fake, it can be bad

A small PCB in a large enclosure
… But not so good inside.

There were elements on the board that I hope for a smaller switch-mode main PSU. Rectifier, electrolytic capacitor, control chip, opto-isolator, ferrite transformer. It’s a through-hole board, and unlike some plug-top chargers, designers have given them plenty of space. Flip it over and there is a reasonably healthy 6.25mm physical separation between the two sides with an extra matching slot at the bottom of the opto-isolator. I can’t comment on the quality of the transformer without evaluating it separately, but maybe it can be a little more chunky.

The board itself may be reasonable, even if it is in a thin box attached to a suspicious hair-thin conductor and protected only by an adhesive tab. Zooming in on the chip I got a CSC7224, a little 18 W 8-pin DIP. It is a generic chip that is available from multiple Chinese manufacturers and it implements a pretty straightforward switch-mode PSU. It seems to follow the circuit quite closely on the data sheet without the main filter, which means it is probably a functional and terribly insecure 12 V supply module. I would be happy if I had a good need for 1.5A.

So I was taken on a journey by a supplier to the other side of the world, and for your entertainment and development I turned it into a hacked article. Props to AliExpress for this, when I raise a dispute over the photo and hardware details, they return without question. What else can I take from this without the warning of not playing random PSU roulette again? The first thing is that, from the manufacturer’s point of view, it is too cheap to be a successful counterfeit product. If I can tell by the weight of it that it’s fake the moment I pick it up, they’ve failed, so I’m curious why they didn’t make it more believable by putting a little more weight on it. At least the chip has overcurrent protection built-in, so it will refuse to serve 5A instead of exploding.

In this way I exposed myself to ridicule in the comments, and obviously I should have given a little more thrust. Have any of you ever been stunned by a fake PSU?

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