Post AzvalijwDyLxfCDPo8 by jpm@aus.social
(DIR) More posts by jpm@aus.social
(DIR) Post #Azvald9azfJOL2Aoy0 by jpm@aus.social
2025-11-05T00:52:32Z
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Alright, time to examine a “LED power supply” that probably won’t kill me
(DIR) Post #AzvaledlSz2QwtIQd6 by jpm@aus.social
2025-11-05T00:55:58Z
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No real distinguishing marks, labels, logos, etc. I grabbed this one in particular because the video appeared to show the necessary line-side safety components. Yeah it’s #StraightOuttaShenzen https://www.aliexpress.com/item/1005006012659800.html
(DIR) Post #Azvalfp949jgcTd20W by jpm@aus.social
2025-11-05T00:58:45Z
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As the video shows, it’s an extruded aluminium case that’s very common on these kinds of power supplies. Push the sides in and the top pops off.
(DIR) Post #AzvalgWOTMKYmbrZQ0 by jpm@aus.social
2025-11-05T01:04:52Z
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And that’s what I spied on the video - a big yellow X-class safety capacitor across the input, and right next to it is a 2A thermal fuse. As a bonus, the blue capacitors behind it appear to be Y-class safety capacitors too!
(DIR) Post #AzvalhCDxpn6sLQycS by jpm@aus.social
2025-11-05T01:11:45Z
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There’s even a milled trench underneath the third Y-class capacitor to separate the line-voltage and ultra-low voltage areas
(DIR) Post #Azvalhz91wvHK4K2s4 by jpm@aus.social
2025-11-05T01:14:04Z
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Better view of the printing on that Y-class capacitor
(DIR) Post #AzvalijwDyLxfCDPo8 by jpm@aus.social
2025-11-05T01:26:10Z
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As for the rest of the board, there’s some kind of coating across everything that makes it all very hard to identify. But it’s pretty unexciting - a full-bridge diode set, switching controller, and either a MOSFET or voltage regulator on the output side.
(DIR) Post #AzvaljUNRJV3zDwVBw by jpm@aus.social
2025-11-05T01:33:48Z
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There’s one interesting trick they’ve pulled though: soldermask openings on the back along tracks, so that the wave soldering process sticks solder to the open areas. This dramatically increases the thickness of these traces, which in lowers the resistance and in turn increases the current capacity.
(DIR) Post #AzvalkMGCybMgL9XBA by jpm@aus.social
2025-11-05T01:39:42Z
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Is the metal case earthed?
(DIR) Post #AzvallN0RgnBowVdyq by jpm@aus.social
2025-11-05T01:56:09Z
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Paging @s0 to the mains electrical crimes phone. Did I miss anything?
(DIR) Post #AzvallU61KSoAvpJ20 by jpm@aus.social
2025-11-05T01:41:03Z
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Yes it is! Paint is an effective insulator…
(DIR) Post #Azvalm6jhfN86luAG8 by jpm@aus.social
2025-11-05T02:00:28Z
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Overall this one appears to be a far better effort than the previous one I opened. Could it deliver its claimed 100W at 24V? Probably, at least for a little while. 100W is only a bit over 4A and well within reason for the design.
(DIR) Post #AzvalmswoPw8WISfPE by jpm@aus.social
2025-11-05T02:10:13Z
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Right, you got all that?ROUND 2! FIGHT!
(DIR) Post #Azvalnjle2BhA7Aqjg by jpm@aus.social
2025-11-05T02:13:02Z
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The MeanWell LRS-100-24. This one has obviously been used as a seat
(DIR) Post #AzvaloSmweCTPkEnuS by jpm@aus.social
2025-11-05T02:14:27Z
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MeanWell have built themselves a deserved reputation as a solid reliable and affordable power supply brand. Their design is definitely inspired by the likes of TDK-Lambda.
(DIR) Post #Azvalp54eIpDKU9NaK by jpm@aus.social
2025-11-05T02:22:42Z
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One screw, and the lid slides out. I should flatten the case back while it’s off
(DIR) Post #AzvalpcOePTozpjzWa by jpm@aus.social
2025-11-05T02:25:01Z
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It looks pretty different to the previous board, because it’s a single-sided PCB. The green soldermask is on the underside. A lot of voltage separation slots milled into the board
(DIR) Post #AzvalqF2KkO8vfoqki by jpm@aus.social
2025-11-05T02:29:57Z
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This one even has a MOV to protect the power supply itself from mains voltage shenanigans! X-class capacitor and thermal fuse again, plus a bunch of Y-class capacitors.
(DIR) Post #Azvalr6D92vHaahJdQ by jpm@aus.social
2025-11-05T02:32:26Z
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It’s obviously designed for a different market - people who don’t fear the hot end of a soldering iron to perform repairs. They printed the fuse model on the PCB, with a suitable alternative!
(DIR) Post #AzvalrnoWvnjlp68bA by jpm@aus.social
2025-11-05T02:36:50Z
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The components used appear to be much heavier-duty than the previous power supply, and they’re all through-hole components which means easy repairs especially on a single-sided PCB. It’s also about 3x the size of the other one.
(DIR) Post #AzvalsSa5MPXoGAh8q by jpm@aus.social
2025-11-05T02:52:07Z
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Now, on to challenger 3?!This one claims an IP67 rating. Let’s see how bad it is inside, because I bought it for being a sealed unit that little kids can’t poke crap into.
(DIR) Post #AzvaltDNHNqE9O444u by jpm@aus.social
2025-11-05T02:56:11Z
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Another extruded aluminium case, and yes it does even have a gasket inside the ends. I just hope it hasn’t been rammed full of potting compound…
(DIR) Post #Azvalu10IrXYdJHhR2 by jpm@aus.social
2025-11-05T02:58:12Z
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… motherfucker
(DIR) Post #AzvalufPsbrmeeByQS by jpm@aus.social
2025-11-05T03:11:52Z
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Because fuck you thats why
(DIR) Post #AzvalvJpSMC0fz6FPs by jpm@aus.social
2025-11-05T03:13:29Z
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Waitaminute that’s a fuse!
(DIR) Post #AzvalvxB63fUe1VfkW by jpm@aus.social
2025-11-05T03:20:17Z
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Brb going diggin’
(DIR) Post #AzvalwhyI56Az9P2ga by jpm@aus.social
2025-11-05T03:33:57Z
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Ok that’s the mains side opened up. The only safety device is a single fuse - earth is connected to the case and the entire PCB is floating in goo
(DIR) Post #AzvalxUBOpfBOfxXpg by SlicerDicer@friedcheese.us
2025-11-05T07:10:54.679633Z
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@jpm Yeeeah buddy that’s like me cutting my dc to dc converter to my Tesla open with steak knife. Always always break it to make it.
(DIR) Post #Azvam7Xk0SS2abhWlc by jpm@aus.social
2025-11-05T03:53:36Z
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Ok that’s cute, I got an impression of the MOSFET in a piece of this goo
(DIR) Post #AzvamFrB64kiNCrAAq by jpm@aus.social
2025-11-05T03:54:37Z
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Hooray, unearthed a Y-class capacitor!
(DIR) Post #AzvamNibroeUkwuQvg by jpm@aus.social
2025-11-05T04:09:08Z
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A couple more impressions
(DIR) Post #AzvamW3SsA5UbwjCXw by jpm@aus.social
2025-11-05T04:39:35Z
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And there’s the DC side opened up
(DIR) Post #AzvameTzXQ3mkXCV0K by jpm@aus.social
2025-11-05T04:46:42Z
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And that’s as open as ICBF making it
(DIR) Post #AzvammeZ9zGw5eD3b6 by jpm@aus.social
2025-11-05T04:49:27Z
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Couple of detail shots
(DIR) Post #AzvamvA3WnDMTd0Jn6 by jpm@aus.social
2025-11-05T05:26:59Z
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How does this one fare overall? Better than the one I opened up a couple of weeks ago, but worse than the first one on this thread. On this one, there is no input filtering - no X-class capacitor across the input and no common-mode choke. Not strictly necessary but its absence suggests a fair amount of cost-optmisation has occurred which is a red flag. Good to see a proper Y-class capacitor inside, but missing a milled-out section between the line-voltage and ULV sides. Interesting design choice for the transformer in the middle to be floating on the goo, achieving the necessary separation between the two sides.
(DIR) Post #Azvan30mLAXypAj1RQ by jpm@aus.social
2025-11-05T05:30:18Z
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And the takeaway message? Buyer beware. If you’re not sure, just buy the Mean Well power supply even though it costs twice as much and is 3x larger for the same power output.
(DIR) Post #AzvanAw6sPZ9P0bPH6 by jpm@aus.social
2025-11-05T05:40:32Z
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Also, what even are X- and Y-class capacitors? They are capacitors that are designed to fail in a specific, known way. X-class capacitors are designed to fail electrically closed-circuit, and are usually placed between line and neutral for RFI filtering purposes. There should always be a fuse or other over-current protection device upstream of the capacitor, and many designs include a fuse on the circuit board itself to be damn sure. If there’s no fuse, then the fail-short will cause an electrical fire. Y-class capacitors are designed to fail electrically open-circuit, so in the event of a failure the capacitor will stop working but won’t let any electricity through to where it shouldn’t be.
(DIR) Post #AzvfWKEHZUMx4Xt3QG by SlicerDicer@friedcheese.us
2025-11-05T08:04:43.670839Z
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@jpm Shouldn’t those fets be on a heat sink?
(DIR) Post #AzvhbAx9ggapeuJgNU by jpm@aus.social
2025-11-05T08:27:21Z
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@SlicerDicer you’d think so. I suspect the grey goo they were encased in has good thermal conductivity.
(DIR) Post #Azvhdlyozeab4hKmpM by SlicerDicer@friedcheese.us
2025-11-05T08:28:29.518349Z
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@jpm Maybe it’s just enough to sink it and not overheat. Just fets get super hot.
(DIR) Post #AzviMrR9YEzZ1x5NWy by jpm@aus.social
2025-11-05T08:36:04Z
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@SlicerDicer they also look like quite big units, and two of them, for the power they’re handling. Probably been significantly de-rated for this application.