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Technical Tips from Mark W. Persons
20 KW Transformer Repair

September 21, 2010:  This photo shows a terminal that burned off a 3-phase high-voltage power transformer in a Gates FM-20K Transmitter.  The terminal was on the 208 Volt primary side of the transformer.  Apparently the crimped terminal overheated and caused the braided wire to oxidize and burn off.

Most of 100 Amperes of current normally flows in this terminal to get a full 20 KW of RF power from the transmitter.     

A 100 Watt American Beauty soldering iron was used to get solder into the braid to get a good connection.  It is not easy to see, but the braid was parted in the center to allow a 1/4-inch bolt through for the electrical connection.  A new hole was drilled in the fiberglass terminal board, above the wire, to allow a new bolt through in place of the one that burned the fiberglass, which you can also see in the photo.  A brass bolt was used and the hardware was tightened and then retightened with the hope that this wire will stay cool. 


The stories go on and on.  Stop in again sometime.  I'll leave the soldering iron on for you. 
Mark W. Persons   ham W0MH      

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