I beg to differ with Duncan Brown. The purpose of

a high voltage loop supply is not to overcome loop

resistance but to build the current up quickly, in

spite of the selector magnet inductance, until it

reaches the value set by the current limiting

resistor - 20 or 60 mils.

Personally I like Ralph Mowery's suggestion - buy the

DC to DC converter on eBay. It is not too expensive and

should ship quickly from the U.S. Just mount it in a box

(for safety), set it for 120 Volts and add a wirewound pot

to adjust the current.

Do what Harold and I do - go to your local Lowe's or

Home Depot for a project box. I am attaching a picture of

my two portable (as opposed to rack-mount) loop supplies.

Tom   N3CRK