Shocking!

[tubesornothing]

A friend has a tube Amp that has an old 2 prong plug and is causing shocks when touch the chassis, and the person touches ground.  I will replace with a 3 prong plugs, but I think the problem is more serious. 


When I measure from chassis to ground, 1 get zero volts when powered off.  Regardless of the polarity of the ac plug.


When I do the same measurement with it powered on, I get approx 70 volts.  One time it showed 350v.


What is my next step in diagnosis of the leaky component?

[sluckey]

Which amp?

[PRR]

It may not be wrong for an UN-grounded amp to show half the wall voltage. That's what it would drift to if everything were equal.

You could be curious and try a 50k resistor to wall ground. Does the floating voltage change?

However a SOLID ground is best, because if a major leak happens it will blow the cellar fuse.

[tubesornothing]

Thanks guys,  I will try the experiment.  This is a jukebox Amp.  I will see if I can dig up a schematic.

[PRR]

...This is a jukebox Amp....

Which amp?