Brokenwood Mystery is it possible?

[ericmark]

Depends what amplifier it is plugged into.

AIUI at least in the USA (no idea about elsewhere) there exit (very old) guitar amplifiers that directly use half-wave rectified mains and so have the signal ground connected to mains neutral. Combine those with a polarity reversal and things could get interesting.

So with those amplifiers likely a type AC RCD would not trip due to DC component, so that would seem to explain the extended time people have felt the shock for.

 

[winston1]

RCDs, called GFI there are not generally used on US circuits anyway. Some sockets in kitchens and bathrooms have them built in though.

 

[ericmark]

RCDs, called GFI there are not generally used on US circuits anyway. Some sockets in kitchens and bathrooms have them built in though.

We also rarely use them with our 110 volt (55-0-55) supplies. Only 5 to 18 volt over what we call extra low voltage. Hard enough to find a yellow brick with an over current device on output never mind a RCD, yes there are some in-line RCD's but when used with mag mount drills they can create more danger than they remove.

 

[JohnW2]

AIUI at least in the USA (no idea about elsewhere) there exit (very old) guitar amplifiers that directly use half-wave rectified mains and so have the signal ground connected to mains neutral. Combine those with a polarity reversal and things could get intersting.

Indeed.

However, as I said/implied before, even if there is a transformer in the PSU it is far from necessary that the output of PSU is isolated from earth - so (with a transformer), although an RCD (of any type) on the mains side would not react to a fault (including through a human being) current between the output of the PSU and earth but, unlike the situation that eric implied when there is an 'isolating transformer', a person touching the output of the PSU and earth would certainly get a shock (if the voltage was high enough).

In decades past (but only rarely more recently), I have built countless transformer-based PSUs, with DC output voltages ranging from 6V to ~2000V but, whether I was using half- or full-wave rectification (usually the former in the early days, when the 'rectifiers' were thermionic valves), one side of the DC output (and the chassis/case of the equipment) was invariably connected to earth - not an issue with 6V, but somewhat more with 2000V !

Kind Regards, John