electric shocks from UM2 ext

[cairn 5]

I know there are a couple of old posts about this issue on the board already, but I'm getting regular shocks from my machine. I even get zapped inserting the SD card.. can't believe it doesn't wipe the data!

I can't believe it's static buildup as it happens every few minutes. Also, never happened before with the machine in the same position, same power outlet, same environmental factors etc..

Anyone know where I should look for a cause?

[ahoeben 1,952]

Is the power socket you plug the power supply in properly grounded?

[cairn 5]

43 minutes ago, ahoeben said:

Is the power socket you plug the power supply in properly grounded?

Same socket it's always been plugged into.. Can a socket become non-grounded? 

[ahoeben 1,952]

It could be that it has never been properly grounded, and something else on the same group has recently started to leak some charge to the ground. Try plugging the printer in in another part of the house (eg the kitchen, which is usually on a group of its own)

[cairn 5]

I'll give that a try.. 

[geert_2 557]

An electric fault could of course be the cause, or a ground-wire with high resistance. Let's say you have a ground-resistance of 25 ohms, and a fault current of 4A (=not enough to trip the fuse), then you would get a voltage of 100 Volts on the ground pin of the socket. However, if this would be the cause, then it should happen every time you touch the frame of the printer, and *as long as you keep touching it*.

 

If it is only a short shock and then nothing, it is static charge which is discharged when touching a grounded frame. So I would guess it is the latter? Maybe due to a change in clothes (wool, some synthetics?), or different shoes? Or very dry and cold weather?

 

Or some other equipment that charges up, which transfers its charge to you, and then you discharge it via the printer and ground? For example old monitors with CRT tube were known for this.

 

Try attaching a voltmeter to the ground-pin. If it is static charge, it will be very hard to measure due to the input resistance of the meter being too low and the charge leaking away. However, if it is a fault, it should be very easy to measure (try both AC and DC).