Powerstat 136B variac wiring ?

[n4wc]

Since I already have this unit I thought it would work to drop my line voltage from 125VAC(24/7/365) to 115VAC.  The basic hookup seems to be pretty straight forward.  This unit only has screw terminals, no plug/receptacle. 
What do I do with the green wire?
Do I just run it from the wall plug to the xmtr bypassing the variac.  My HT-20 has been modified to 3 wire with the hot ac going to the fuses then the switches then the power xfrmrs.
Should the variac chassis be connected to the green wire?
Appreciate any help.
Thanks
N4WC Bill

[KA2DZT]

Yes,  you connect the ground to the frame of the variac.  You'll have to find a screw somewhere to use for the ground.  Variacs and Powerstats were made many different ways so right off I can't tell you what screw to use. 

Fred

[KA2DZT]

Bill,

If you are putting the powerstat in a housing or metal box you would then ground the line cord green wire to the housing.  The powerstat would then be grounded to the metal housing by way of its own mounting bolts.  Your AC output outlet would also have its ground terminal connected to the same ground point as the line cord.

Hope this helps,

Fred

[WBear2GCR]

If ur going to keep it as a fixed stepdown, you might consider using an isolation transformer with taps rather than the variac. The variac provides no isolation and having isolation can be an advantage.

Just a thought.

               _-_-

[n4wc]

Thanks for the input.  This setup works great!  The spec'd 807 modulator plate voltage is 700 and it measures that at 113.5AC input.   It was slightly over 800 volts with 125AC input.  A couple of chassis screws near the variac front panel were available for the ground wire(green).

The idea of a switchable transformer sounds nice.  Where might be a good source.  I suppose I could have one wound; it would be like a bucking xfmr system.  This HT 20 is ~500 watt draw on max output.  I don't have a xfmr
junk box so it would have to be 'kinda sorta new or new old stuff'.
I really like the idea of multiple taps.
Thanks
Bill N4WC

[WBear2GCR]

New you can buy them from Signal Transformer company.
Good to look up theirs for reference.

Ebay is a source too. Shipping could kill you though.
One sees them at hamfests too.
I've pulled some out of dumpsters, but that's not reliable.

What ur looking for is an isolation transformer with either primary and/or more
usually secondary taps. Rated at a KVA above ur load.

Oh, DIY thought, you could wind ur own secondary on a toroid, or unwind the secondary of a toroidal isolation transformer. Another idea is to add turns to a toroid that is shy of the target voltage. (toroids with 48-0-48 and 56-0-56 windings are reasonably common, used in various applications including audio power amplifiers)