Re: [Harp-L] maestro

[fjm <mktspot@xxxxxxxxxxxxxxxx>]

Eric Neumann writes:

> sounds to me like a simple non gounded ac power plug... but a good tech will be able to sort that out. An electric shock can be very serious - so don't use the amp if it shocks you... pretty much a bad thing.

In response to:

>  Anyway, the guy I got it from said he thinks it is an early 60's vintage. Sounds good but it does have a short somewhere-will sometimes shock you when you grab a switch.

While replacing the plug with a grounded one will most likely solve the 
problem it's not the ground that will solve it.  It's the fact that 
grounded plugs are polarised and will synch your amp with the rest of 
the correctly wired world.  Incorrectly wired outlets will possibly pose 
a problem.  The shock happens when you touch your chassis and something 
else in the room that's wired oppositely.  The voltage is getting to you 
via the coupling capacitors which are wired to ground or tha amp chassis 
on one side.  They're tiny, they can't let very much amperage through at 
a time.  I did the math on the amperage potential once and it was micro 
amps which are even smaller than miliamps.  It's annoying but not likely 
potentially life threatening.  If there really was a short to ground  in 
the amp fuses would burn breakers would trip and metal would be melted. 
 As an experiment I plugged both of my non polarised plug White 
amplifiers in oppsoitely and tried like heck to get a gfci outlet to 
trip.  I could not do it, shocked the heck out of myself but the gfci 
wouldn't go.  It's that small. It's below the trigger threshold of a 
gfci.  As always with electrical devices, never swim with them plugged 
in, dont use them in bathtubs and if you don't know what you're doing 
consult someone who does.  By the way the cheap fix for this problem is 
to pull the plug out and reverse it if you're getting shocked.  I 
finally just marked one side hot and plug it in correctly but this fix 
requires some electrical knowledge to be succsessfully employed.  fjm