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Collins S-Line Preselector Tuning
Copper Band Repair

Written By: William E Harris / K5MIL

 

 

One of the copper bands on my 75S-1 receiver finally decided to give up and break.  There was quite a bit of discussion on the Collins Reflector recently about how to do a repair, with several suggestion being made.  I decided that a repair should be as close to the original as possible.  At a local surplus house I found large roll of 5 inch wide thin copper sheet that had quite a bit of spring to it.  The owner didn't know for sure if it was beryllium copper and I couldn't really tell for sure either, but it seemed to have enough spring that it should do the job.  The price was .$90/ft, so for a dollar, I got enough copper sheet to do more preselector bands than I will probably ever see. Below is the step-by-step procedure I used and I am pleased with the results.  I think if I had to do another one or two the results might be even better.  So I hope this might be of help to someone else attempting such a repair.

 

The preselector tuning rack removed from the receiver showing the broken copper band.  To remove the rack, remove the knob from the shaft.  Make a choice to either remove the tuning slugs or leave them attached.  As can be seen, I did not remove the tuning slugs, which made me a bit nervous handling the rack.  If I were to do this again I would probably remove them just to be safe.  Next remove the four screws that hold the rack to the chassis, one in each corner.  Gently lift the rack from the chassis, being especially careful if you leave the tuning slugs attached.

 
 

I drilled a small hole in the frame so I could insert a smaller drill, and drill out the brad that holds the copper band to the tuning slug rack.   If I were doing this again, I think I might try using a Dremmel tool and grind off the top of the brad instead of drilling.

 

 
 

The copper band has been removed and all the pieces placed back together and held with clear tape.

 
 

The copper band is placed on the sheet of copper and held in place with another piece of tape. An Exacto knife was use to scribe around the old band.   By placing one edge of the band along the edge of the copper sheet meant only one long cut with the scissors had to be made.  The holes were also marked at this time.

 
 

Next scissors were used to cut the new band from the copper sheet.  The holes were made by placing the band on a soft wood block and using a punch and hammer to punch out the holes.

 
 

The end eyelets that hold the spring clips were cut from the old band and placed in the holes on each end of the new band and soldered in place.  See next picture.

 
 

Eyelet soldered to the copper band.


 
 

New band ready for installation.

 
 

The new band installed.  I found the easiest way to install the new band was to loosen the nut on the back of the rack frame, back out the set screw that holds the metal rod centered.  This lets the rod drop down so that the spring tension clip can be easily installed into the eyelets, then pull the rod back into position and adjust the set screw back to its original position.

 
 

The assembly re-installed in the receiver.   A 4-40 screw and nut were used to secure the slug rack to the band in place of the original brad.

 
 

Another view of the new copper band.

 
     

 

 

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