Tingles from power supply

Apparently it's normal, and is related to RFI suppression.

Sylvia.

Sounds like a small cap from mains.

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It's certainly not a happy thought. I will be treating the low voltage side of such power supplies with more respect from now on.

BTW, I tried the same tests with the power supply for my cable modem. It showed higher voltages, but lower current.

But immediately after I'd unplugged it from the mains, I happened to touch the mains plug pins with the palm of my hand, and got a significant shock off it. Reverse leakage through the rectifiers? But why should there even be enough to feel?

Sylvia.

That is also quite normal ! There is one or more capacitors across the supply pins. They can be left in a charged state at the instant you pull the plug.

The voltage you measured on the output side was simply due to the leakage capacitance of the transformer or if a switch mode psu the capacitors on the supply side having a connection to the common rail.

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Do you mean a *real* Avometer Sylvia? As in model 7 or 8?

100 uA is usually below the threshold of sensation (usually about 1 mA), but some people can sense current of lower value. If it has a three prong plug, it may have capacitors to ground. There is also some capacitance from the primary to secondary windings, especially if they are layer wound. The shock you got from the plug after disconnecting from the mains may have been from an RFI filter capacitor that was still charged. If you touched across two blades of the plug, that might explain it. If you only touched one blade, then there must have been another return path to ground, such as the secondary output to a chassis ground, and you would have had to touch something else grounded, or be wearing very conductive shoes. If it is a switching supply, there is a fairly large electrolytic charged to about 180 or 360 VDC, and maybe there is reverse leakage through the bridge rectifier. You might check for DC voltage on the mains plug blades after disconnection.

Paul

Use some common sense. Oh, that's right, you do not have any.

Look at how stupid your question is, and you will already have your answer.

You're an idiot, and it is related to your 100% lack of grasp of electronics.

Please do us all a favor and latch on to the high side of one soon.

You're a total retard, and you likely do not even know how to make such measurements.

Damn! Obviously not significant enough!

You're an idiot. You don't even know what type of circuit the dongle is constructed with. You won't know either, until you pull out the dremel tool, and stop guessing like the twit you are.

100% correct. It'll almost certainly be a Y2 cap between the live and secondary sides of the switching transformer.

Go to powerint.com to find out why it's there.

Graham

On Mon, 09 Mar 2009 02:18:22 +1100, Sylvia Else put finger to keyboard and composed:

See this DVD player PSU circuit:

Notice capacitor C8 at the top LHS. It is a Y1 type that connects the the primary common to the secondary ground. That's what is giving you the tingle.

IME TVs often have a high value resistor and capacitor linking the reference points on both sides of the switchmode transformer. For example, my Sanyo TV has a 5.6M resistor and two 2200pF caps between the negative terminal of the main 400V filter cap on the AC side and the 0V reference on the DC side.

|---- R ----| |- C --- C -| _|_ _|_ = ===

This article talks about X and Y line-filter capacitors:

- Franc Zabkar

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Switcher front ends have transformers? Are you mixing your power supply designs in your head, boy?

Do the math on the cap and find out that even "fully charged" it will not present the scenario she described. You are all f****ng loony tunes if you think it does.

You haven't the tiniest idea what you're talking about. You clearly have NO KNOWLEDGE of either safety issues or EMC.

Graham

I did try immediately afterwards (after plugging it in again for a bit). Couldn't see much. But it may be a time issue - it's possible to get one's hands onto the pins rather more quickly that a pair of multimeter probes. Depends how long the capacitor would remain charged with no output load.

Further experiments using my hand might be informative, but I'm not game.

Sylvia.

You're full of shit. I have incorporated more x and y caps into my designs than the number of designs you ever did.

Like I said before... I have designed power entry modules. You are clueless about them or you would have shut the f*ck up the first time I told you about it.

I have designed both HV Xray supplies for LANL as well as medical supplies where human contact meant limitations in output and it had to be exact.

You're a goddamned idiot that makes retarded assumptions at every turn. You are nothing more than a retarded donkey that should get slapped on the ass while at the edge of a cliff. Fuck off, you retarded, old, know nothing fart.

And I'm God.

Oh, wait a moment, I can't prove that either. Bummer.

Sylvia.

I do not have to prove anything, you stupid cunt. What I can prove is that by the content of your posts, you are 100% retarded as to how things electrical and electronic work.

The fact that I DO know what an 'entry module' is, and that he did not further proves that I know more about it than the retarded donkey ever could.

But you HAVE !

You've proven a total lack of understanding of wall warts.

Graham