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Radio Broadcast Technical Consulting and Sales
10032 Island Drive, Brainerd, MN  56401


Technical Tips from Mark W. Persons
AM Coil Cleaning

After many years of use, silver-plated coils can become very black with silver oxide. The coil on the left is an E. F. Johnson, built in the 1950's or 1960's.  The coil on the right is of the same vintage and looked much like the left one, but has been cleaned.  The coil surface is not perfect, but is so much better than before the cleaning process.

Coils are then ready for years more service in an AM transmitter, AM antenna coupling unit, or AM phasor.

We have found that Muriatic Acid will do the job.  Because the acid is toxic, we do the work outdoors and use rubber gloves when handling the coil in the acid bath.  To do the work, the coil ribbon is removed from its coil form and is put in a plastic bucket with about 2 inches of the acid in the bottom.  It takes about an hour to clean a coil when the coil is turned every 15 minutes.  Best to wash the coil in a bath of water and baking soda to neutralize the acid and then rinse well.   

Muriatic Acid is available in well-stocked hardware stores for about $6.00 per gallon.

We have a number of used coils on hand for sale.  

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

Questions?  Email Mark Persons:  teki@mwpersons.com         

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page last edited 02/22/2016