Crappy mains adapters & crappy designs

We sell a few little boxes that are powered from a 12-volt wart. We always start with a polyfuse, followed by a 15 volt transzorb, which also gives reverse polarity protection.

John

Looking at these I suspect they are using a series cap to reduce the voltage to the transformer.

The WAPs no longer work with a good PS?

More to the point, the equipment might be nice, but management decided that a power supply was a commodity item to be sourced from China - though I suspect your entire units were made there.

I have a very expensive, now very obsolete, US-made networking box that does some esoteric processing which lets us run a segment of network over a wire that would not otherwise run it. One day it stopped working. I eventually figured out that the cheap-Chinese power supply had crapped out (this was not overly obvious since the lights were still on, as it was not dead on all 3 voltages).

I pulled an old clunky linear supply from the junkbox and spliced it into the connector, even though the unit was still under warranty. If I had gotten the warranty replacement, it would have been the same crappy quality, and my tolerance for that is limited on boxes that cause much crying out and gnashing of teeth when they break. I did inform the company of what I had done, and why, but got no response from them.

With all due respect that does not look like stuff from a respectable firm. There are wall warts from reputable sources such as Condor/Ault but it seems this "respectable firm" might have cut a corner here and saved a buck.

Check out SMC. I've got their Barricade router here and it has a built-in switcher. Nothing gets hot, ever. It's totally cool to the touch. Imagine, a built-in power supply. Wow. What a concept. Guess people slowly figured out how grandpa's tube radios were designed and why they last so long.

Oh, BTW, that Barricade router has a full metal enclosure. None of this plastics stuff. Byu some real industry-grade gear and you shouldn't have that problem. If it has a wall wart look for something better. If it has a cheap wall wart, run.

what's the 400V electrolytic capacitor for then?

As I read it the small yellow box and the tranformer looking thing are a capacitor across the input and a common-mode choke, the large yellow box is the transformer

yep.

I've pulled a fair few of these to bits. the construction ranges from excellent to appalling.

The trick is to stick to a reputable manufacturer.

The problem is without a hacksaw, you cant see what they are like!

Meanwell make reasonably good stuff.

Cheers Terry

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How about doing us all a favor and naming names?

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Not Cisco Systems (Linksys)? I plug mine in a good quality powerstrip that has surge protection and all the bells and whistles no problems so far...

And it's only going to get worse with new government standards for higher efficiency wall warts! Unless of course, these same Standards weed out all the incompetent designer wannabees. But I doubt it.

I think the California law goes into effect this year??

-mpm

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Well, in fact the 4 units are from Linksys placed in different locations in a building on different mains groups (2 powered from a UPS).

I tried that, but no go.

It looks too small for 50/60 Hz unless it's an SMPS in which case it gives me no confidence.

Of course, if you know your mains are crappy, you should have upstream protection for the wall warts.

That's a really crappy UPS that let something through that wasted something dowqnstream.

Or crappy power supplies that barely hung on and then collapsed. I have seen some horrible "designs" where stuff had turned brown just from normal operation. Others had 300V devices on directly rectified mains and were marketed in Europe, meaning their ratings were exceeded even under perfectly normal line conditions. Then there was one that got freaking hot and the mfg said it was normal. One fine day the ambient temp went a wee bit above 30C and ... POOF.