noise filter/ iso transformer question

[kenzo42]

hi everyone,

my japanese cabinet's AC plug doesn't have the middle prong (i believe it's called an earth ground?). i noticed in bob robert's basic wiring that the middle prong ground IS used at the noise filter.

does the noise filter need to be grounded if i'm adding an isolation transformer to the cabinet?

thanks

[Grauwulf]

Yes, your cabinet should be grounded.

[Ken Layton]

A niose filter won't function without a ground connection. Remember that a noise filter's purpose is to shunt the noise to ground. No ground = no workie.

[kenzo42]

that's interesting b/c my cab doesn't have the middle earth ground prong on the ac plug (2 prongs total). does this mean that all japanese cabs that don't have earth ground prong have non-working noise filters? please take a look at this picture:

http://pg.photos.yahoo.com/ph/liu_feng_yi/detail?.dir=cb97&.dnm=2369.jpg&.src=ph

it almost looks like the noise filter is upside down?

[MonitorGuru]

It's probably grounded through the 2 screw tabs. Notice the green pair of wires screwed into the metal plate lower in the picture.  The noise filter might be electrically conductive  between the ground pin and the two mounting screw flanges (Take a multimeter and test for resistance between them after detaching the wires from it to be sure)

In any case, if you dont have a ground pin on the cord, GET ONE. For safety alone.

Perhaps in Japan they don't use them and assume neutral == ground, but in the U.S. that is not safe for any product that has ANY electrically conductive exposed material (e.g. metal coin door, power switches, etc..).. it must all be grounded for safety.

[Ken Layton]

In Japan the cabinets have an "Earth" screw on the outside of the cabinet near the power cord entrance. It is intended for a seperate ground wire to be connected from either a power outlet wall plate ground wire connected by the location or business owner.

[kenzo42]

so could i just replace my current 2 prong power cord w/ a 3 prong power cord extension, with one end chopped off? or is there some converter?

i'll be using a step down converter 120v -> 100v btw.

thanks.

[gearguy]

As long as you have it earthed you're fine - whether or not you chose to do this by using a 3 pin cord or not is up to you - you can use the earth screw as mentioned above.

[kenzo42]

is there a place in american homes that have power outlet wall plate ground?

[Ken Layton]

The screw that holds the wall plate is ground.