Computer started putting out EMI

The PSU filter? Power strip? Swapping those with known good ones will narrow it down.

I agree, even though the unit was hibernating, the PSU is still operating a standby supply to keep the system looking for a wake up. The switching supply might be operating right in that freq range and some of the filter caps might be getting a little flaky and acting like little inductors pumping out some EMI.

Also check that the chassis ground connection is still intact. This could be a safety issue.

My newest machine has wake on USB which is really cute. It seems to leave the pointing device and keyboard powered so it can detect changes.

Hey, I forgot about that. Maybe somebody made some BIOS changes or some M$ patch made some changes to the hibernate mode and some peripheral is being kept alive that wasn't before and 'it' puts out some garbage when it is in that state/mode. That's the problem with an issue like this, it could be SOOOOO many things. One of those, "How do you eat and elephant" moments.

On a sunny day (Thu, 4 Mar 2010 09:01:24 -0600) it happened "amdx" wrote in :

I have an old AT power supply that I use as 12V power source, on CB (27 MHz), sometimes a carrier appears. Long time I thought some joker was playing, a strong carrier, it slowly shifts into the channel, hangs there, and then shifts frequency out again. I finally I noticed that when I switched that PSU off, the carrier was gone. It turned out to be an harmonic of the switching frequency.

Maybe also in your case? Temperature variations or load variations can move that harmonic around.

Or some electrolytic in the power supply is beginning to dry up.

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Geeze! You make elephant stew:

You need: 1 elephant.

100 pounds of potatos 50 pounds of carrots 75 pounds of green beans 25 pounds of onions 55 gallons of Jack Daniels and a large pot.

Cook for 8 to 12 hours over a low heat. Serves about 500 people. There will be no leftovers, but lots of sleepy drunks.

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MMMMMMMMMMMMMMM, elephant stewwwwwwwww..........

Beginning to dry up wouldn't explain a sudden change, but splitting open like a grilled weenie and spilling out electrolyte could. ;-)

Probably the Vstby switcher circuit. I had one go on me recently. The rest of the supply was good (5, 12 volt rails). Was a 80 plus supply, replaced it with a cheap 500w job with PFC from Officemax.

Cheers

Oh yeah, and that would warrant a peek inside before something goes kablouie during a hardcore design session.

But even a weakening cap can cause such effects. Often there comes a point where a regulator loop cannot hang on anymore and goes a bit berserk.

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This PS is new about a year ago. The back story; power supply crapped out. ordered new one, installed new one and had EMI. Company sent out higher power supply as replacement, that has worked great for a year. This morning it was causing interference, at 3:00pm checked and didn't have interference. Mike

On a sunny day (Thu, 4 Mar 2010 18:50:34 -0600) it happened "amdx" wrote in :

That is pretty much the effect I had with the drifting harmonics, sometimes there, sometimes not. Depends on temperature and load here. Funny, I had not seen that effect for several month, and now it was back last week and still here. Did you run any cables differently? That seems to make lot of difference here on CB. And not only on CB, I found a way to reduce hum in my audio power amp by twisting the ground wire one turn around some wall wart, that induces opposite phase hum, and silences any hum picked up from the inputs.... Joerg will appreciate things like that I think:-)

The proportions are wrong; you need either 1/10 elephant or 10x=20 everything else. Sleeping 5000 and providing waste disposal (including=20 body process needs) for that party is a bit daunting.

Do you recommend peeling the elephant first, and if so, using what utensil? :)

=A0Mike

Could also be something related to power quality, and it just happens to show up near the computer's P/S. I'm thinking dimmer switches, and other doo-dads that alter the AC duty cycle (power under the curve). The computer itself may be doing this?, or you could have something else on the branch circuit that makes it audible (if the noisemaker was always present, whatever it turns out to be).

I'm pretty sure I saw an elephant peeler at Williams-Sonoma.

If not there, surely at Sur la Table :-) ...Jim Thompson

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