Shock from USB printer cable

Sep 11, 2004 21 Replies

Keith Weisshar wrote: : There is even a slight buzzing sensation when rubbing a finger across the : USB connection with just a very light touch and it goes away when the : printer is unplugged. Have you had this happen with your printer?

Congratulation to Keith:

Top quoting 300 line up 9 levels deep to add some few lines....

Argh!

Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt --------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

This absolutely should not happen. There's not much difference between a shock you can feel and a shock that can kill you. Either the power supply is defective or the outlet that it's plugged into is miswired. (Probably the former.)

We should no longer be discussing whether it is normal or safe. IT IS NOT. We should be getting it fixed.

What I'm guessing is that in the printer power supply, there is leakage from

120V AC to ground, through a high enough resistance that all of the leakage gets absorbed by the (correctly functioning) ground connection of the computer when the two are connected together. There are also other possibilities.

When Tech Support mentioned 10 mA they were probably talking about the ability of USB ports to supply 5-volt power to other devices... completely irrelevant.

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