aeio prodded the keyboard

I noticed a tingling from contact with a USB lead of an external
Hard Drive.

Investigating this led to the PSU, the plug of which has a high
voltage on the outer connector compared with house earth. It was
varying between 70 and 110V.

(I did not check the voltage of the output which I have no reason to
doubt was correct - 12V I think it should be)

The PSU is a three pin plug. Presumably the earth connection is not
being used.

Is the PSU faulty?

Check the outer shell to earth pin with an ohmeter.

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Best Regards:
Baron.