[Amps] Alpha 87A Power Supply Question

[Jeff DePolo]

> So I unplug the
> Alpha and perform a continuity check from Leg 1 of the plug to the chassis
> of the Alpha, Leg 2 to the Chassis and Neutral to the Chassis.  As for the
> 120Vac Legs, there is no continuity to the Alpha Chassis.  But there is
> direct continuity from the Neutral of the 220Vac Alpha plug to the Chassis
> of the Alpha.

Unless it's been modified, an 87A shouldn't have a neutral, just two legs
and ground.  

What kind of plug and receptacle are you using?  Are they 4-pole (L1, L2, N,
G), or 3-pole?  If the latter, unless you are using something like an
old-style clothes dryer or electric range receptacle or cord, you should  be
using L1, L2, and ground.  Older receptacles and cords for clothes driers
and ranges used a 3-wire cord using L1, L2, and N, the N being necessary for
powering electric clocks, a range-top receptacle, etc...  There still exists
an exception in NEC for bonding the neutral from the cord to the chassis of
the appliance if you are connecting a newer 4-wire appliance to an old-style
3-wire receptacle, but it is not code-complaint to install a new 3-wire
receptacle using L1, L2, and N.

Based on your description, it sounds like the way it is wired has the
neutral grounded through the 87A frame, which is obviously bad in many
regards, with the hum in your speakers being least of them.

					--- Jeff WN3A



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