Band Switch Repair

    Band Switch Repair
By Walt Cates, WD0GOF

SR-150 THRU 500

Just looking at the switch it seems to be a formidable task. However it turns out to be rather simple yet somewhat tedious for some operations. In this case I had a bad detent assembly on the SR-400A. It was very "soft" and would not hit in the center of the tabs and sometimes stop contacting two positions.

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Fig 1

The first step is to slide the plastic coupler toward the front panel until it is clear of the switch shaft. Start with the switch fully counterclockwise and BE SURE NOT TO ROTATE the switch shaft once de-coupled.

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Fig 2

If there is a SO-239 mounted on the rear panel you will have to un-mount it and move it to the side.

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Fig 3

Now you can reach thru the hole in the rear panel with needle nose and gently pull, WITHOUT ROTATING, the shaft to clear what ever wafer you need to work on. In my case I just needed to clear the first wafer. If you are replacing a wafer remove the faulty wafer noting rotor position, reinsert the shaft and install all hardware before making connections. If you are replacing the detent assembly you may run into your first difficulty. The shaft coupler comes in several lengths. If Hallicrafters happened to use the long coupler you will not have enough clearance from the detent shaft to the first wafer switch to get the detent assy out. Exacto makes a handy little saw, extremely sharp, works fine when forced to use short strokes. Cut off just enough to expose the end of the shaft of the detent assy when it is moved as far toward the front panel as it will go.

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Fig 4


If the coupler is not snug on the detent shaft or the wafer shaft it should be replaced.

If the detent shaft and the switch shaft are not perfectly aligned the coupler will often creep one way or the other. In this case drill a hole thru the coupler in the center. Then after assembly, position the hole over the space between the two shafts and insert a pin.

Just a left over photo.

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We havun sum fun now. Walt, WD0GOF

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