Hi
I noticed that my Toshiba Satilate laptop power supply must be producing EMI when there is not a good connection. There is a good DC connection because it doesn't cut out or anything, but while listening to an AM radio station, a piercing squeal begin coming from the radio. After some frustration, I noticed that it was related directly to the power connection to my laptop because when I press it in tighter, it goes away. Also if I unplug it from the computer, the noise in the radio changes pitch and sound. I have had this puter for a couple of years so the connector may be a little worn out. Has anyone else had problems like this and should I replace the connector jack in the computer or just forget about it? Other than high frequency noise pollution, do you guys think is there any potential problem here?
I think maybe there is some resistance from oxidation on the connectors that maybe changing the impeadance the power supply sees. Maybe just a cleaning is needed.
I noticed that my Toshiba Satilate laptop power supply must be producing EMI when there is not a good connection. There is a good DC connection because it doesn't cut out or anything, but while listening to an AM radio station, a piercing squeal begin coming from the radio. After some frustration, I noticed that it was related directly to the power connection to my laptop because when I press it in tighter, it goes away. Also if I unplug it from the computer, the noise in the radio changes pitch and sound. I have had this puter for a couple of years so the connector may be a little worn out. Has anyone else had problems like this and should I replace the connector jack in the computer or just forget about it? Other than high frequency noise pollution, do you guys think is there any potential problem here?
I think maybe there is some resistance from oxidation on the connectors that maybe changing the impeadance the power supply sees. Maybe just a cleaning is needed.
This may be too raw info for some to handle but here the truth about those type of power supplies.... I had many years in designing/consulting those cheap supplies as well as doing EMC engineering...
Most of those supplies are designed by monkeys who call them selves engineers, mostly in the far-east...
They tinker and play with the values until the power supply somehow doesn't blow up anymore after blowing up uncountable number of supplies...they don't understand loop analysis and don't use any math when designing these things, they just copy values from various data sheets....
Usually when these things are finalized, they have poor phase margin and the magnetics runs extemely hot.....
Then all they need to do is make just ONE unit pass EMI testing...
SO they keep monkeying with input caps, ferrite beads and tons of shielding till they get that ONE unit to pass.... Once that ONE unit passes from a testing company that lets them slide by, usually a relative works in the testing company or they take money... Then the production run of power supplies can be whatever they want, since going back to the first design is called a revison...no need for retesting..there are lots of ways around this...especially if they claim to submit a supply that is thier highest power ratting, then if that passes, then all thier lower power units of the same design automaticaly get passed...
These sub-contractor companies constantly shut down and spring back under new names.... This avoids law suits when these power supplies burn up and take down someone's house...
So don't be surprised if the EMI is out of control....
These companies simply will not pay a real engineer to get the design done properly or with descent parts... many times they will copy a competitors supply and copy the mistakes as well...
This industry is always getting by on a thread and some luck...
cerrem
Most of those supplies are designed by monkeys who call them selves engineers, mostly in the far-east...
They tinker and play with the values until the power supply somehow doesn't blow up anymore after blowing up uncountable number of supplies...they don't understand loop analysis and don't use any math when designing these things, they just copy values from various data sheets....
Usually when these things are finalized, they have poor phase margin and the magnetics runs extemely hot.....
Then all they need to do is make just ONE unit pass EMI testing...
SO they keep monkeying with input caps, ferrite beads and tons of shielding till they get that ONE unit to pass.... Once that ONE unit passes from a testing company that lets them slide by, usually a relative works in the testing company or they take money... Then the production run of power supplies can be whatever they want, since going back to the first design is called a revison...no need for retesting..there are lots of ways around this...especially if they claim to submit a supply that is thier highest power ratting, then if that passes, then all thier lower power units of the same design automaticaly get passed...
These sub-contractor companies constantly shut down and spring back under new names.... This avoids law suits when these power supplies burn up and take down someone's house...
So don't be surprised if the EMI is out of control....
These companies simply will not pay a real engineer to get the design done properly or with descent parts... many times they will copy a competitors supply and copy the mistakes as well...
This industry is always getting by on a thread and some luck...
cerrem
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