Dataman-40Pro: power supply issue ?

[CRi]

Hi everyone,

I have just bought a Dataman-40Pro eprom programmer and I'm having some problems with it.

The first time I connected the programmer, everything went fine. When I disconnected it, I felt an electric shock (I was touching the case of the computer and the USB cable coming from the programmer). The second time I connected the programmer, it was dead, not recognized by Windows (USB device unknown) !

Upon further investigation, I discovered that the negative side of the power supply is floating at 85V AC above earth potential!
I measured a 85v AC potential between the ground of the usb cable coming from the Dataman and the case or usb ground on the computer side.

I ordered a second unit and the symptoms are exactly the same !
Dataman support basically told me "that's ok, it's how floating PSU work"... but I'm clearly not satisfied with this answer.

What do you think, is it defective ?
If that really is "how it's supposed to work", what can a do to prevent it to break again?

Thanks in advance !
CRi

[denelec]

I checked with my desktop computer and there is continuity between ground, the case and the negative (black wire) of the power supply.
That's what I expected.

But my MacBookPro has no ground connexion. And the plug is not polarized.  So it's floating.

[CRi]

Hi denelec, thanks for checking !
My computer is a dell notebook and it is grounded...

The problem comes from the dataman PSU that is floating.

Can I safely connect the Dataman case to earth? Or am I going to encounter earth loop issues?

[CRi]

No one has any idea about his?