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MIDI electric shock - normal?
#1405478 03/28/10 11:35 AM
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I have a Kawai CA-61. The other day I connected the 'USB to Host' to my Windows PC and was able to communicate OK with Finale 2010. While fooling around I touched the USB plug at the back of the DP and I got an electric shock. Not too strong but enough to feel it - not my imagination. I've used very many USB devices over the years and never felt something like this. In all other aspects the DP is fabulous.
I immediately turned off the PC and DP and unplugged the cable. I'm not planning on using the DP as a midi controller. I have just ordered an M-Audio Oxygen 61 for that purpose.


Jose
Kawai K5 - Kawai CA61
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Re: MIDI electric shock - normal?
JGonzalezGUS #1405554 03/28/10 01:06 PM
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I wonder if it might just have been from static electricity discharge when you touch the grounded part of the DP, instead of an actual shock caused by anything high voltage from the USB port, because there's no high voltage output from USB as far as I know.

Re: MIDI electric shock - normal?
Volusiano #1405565 03/28/10 01:23 PM
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I have a Kawai CP136. This doesnt have protection earth. It has a protection isolated transformer inside. Protection isolation means, there are very thick isolated layers between the power windings and between the internal low-voltage windings.

With such a device there is no possibilty to get a schock, when there is nothing dangerously damaged. Possible Damages can be: Maybe a wire inside got squeezed and got contact with other metal parts. (Just for example) However it must be said, that all wires that have dangerous voltages are double isolated and separated from the other wires. Also the are very short they go directly to the mains switch and to the transformer. All other parts of the piano have no dangerous voltages, especially all outside connectors including USB are low-voltage and secure.

I had my CP136 open and looked inside and I can say this has absolute reliable, fine and solid build quality. So I dont believe, that something is defective.

But to be sure consult a qualified person to check it, maybe measure the insulation or check the connections inside.

BTW, if you where connected to another device or maybe the USB cable was connected to a computer or maybe you where statically charged, I would look for the problem there first. Especially computer power supplies are quite often of poor build quality.

Remark: I am professionaly qualified, therfore I know this.
However, each country might have other power supplys and other voltages. Each country might have other standard procedures which are obligatory to check security. There is special equipment to check isolation and any device is build in a way that it will survive this check, if not defective, and so every qualified person in your country can check it.

Peter

Last edited by hpeterh; 03/28/10 02:10 PM.

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Re: MIDI electric shock - normal?
hpeterh #1405767 03/28/10 06:06 PM
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I'd have to say the thread title is both wrong and misleading, what is being discussed is USB electric shock and not MIDI electric shock. AFAIK based on my understanding of DIN midi ports and cables (opto isolated aren't they?), electrical shock on a DIN MIDI cable would be extremely rare and require that something be broken and far out of spec.
Clyde


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Re: MIDI electric shock - normal?
wildpaws #1405781 03/28/10 06:28 PM
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You are very right, Clyde. I had not thought about it that way. Sorry.
Thanks Volusiano and Peter for your replies. It may have been caused by static electricity - don't know for sure and I am not inclined to further testing smile
The room is carpeted, I was shuttling the 12' back and forth between the DP and the PC and because the carpet is brand-new I was bare-footed...


Jose
Kawai K5 - Kawai CA61
Re: MIDI electric shock - normal?
JGonzalezGUS #1405892 03/28/10 10:06 PM
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If you are getting that kind of static around your gear. Then you might want to treat the carpet. Static can destroy electronics. I think there is some stuff you can spray or work into the carpet

It had to be static, there is only 5V DC inside the USB cable and even then it us protected by a grounded shield. The shock you got was almost certainly from you to the USB grounded shield.


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