Shaft Coupler Mounting

Installing 6mm couplers

The 6mm shaft coupler is a simple piece, but can be difficult to install.  Since most buyers will be installing this on the shaft for the Bandswitch, that is what we will cover here.  It’s a somewhat tight fit to get the coupler in for the 820, 530, and 830 versions.

You need two allen wrenches- a 1.5mm to remove the old coupler and a 2mm to install the new one.  It’s best to have long wrenches, with the screw driver handle.

Pull the final cage cover and discharge the HV caps by grounding the lug at the top of the choke coil between the two 6146’s.  Make sure you have completely discharged the caps!!

Remove the 6146 toward the front of the radio. 

This is the bandswitch coupler looking in from the side of the cage on an 830S. Tight fit. The two metal bands that frame the coupler in the photo are the mount for the bandswitch. You can see one of the two screws that mount it to the cage. You can loosen these screws with a right angle screwdriver (Harbor Freight) which will help if you can’t get the coupler in and on the shaft. Just loosening them will give a lot of extra play in clearing the coils on the RF board.  You can remove them if need be.  Just put it all back when you’re done.


Look in from the side and you should be able to see the coupler and it’s set screws.  Watch it while you rotate the bandswitch.  You’ll notice that the shafts have flats on them.  Two setscrews will be on the flats, two will be on the rounded part of the shaft.  Rotate the shaft so that you’re looking in on the setscrews for the rounded part of both shafts.  Loosen those two screws.

Now, rotate the shaft so that you are looking at the flat on both shafts.  Loosen those two set screws, note which band the knob is pointing at, and pull the shaft by the knob, a ways out of the coupler, but not all the way, just an inch or so.  When you reinstall, the flat on the shaft will automatically align everything.

Getting the old coupler out can be a problem.  If it won’t go through the hole, you can reach in with some cutters or an exacto knife and chop it into a couple of pieces which you can then fish out with some forceps or long needle nose.

I like to have the allen wrench magnetized a little, which you can easily do by touching it to a magnet for a few seconds.

You can now slide in the new coupler.  If it’s too tight loosen the two screws that hold the bandswitch mount from the front of the cage.  I like to do it with the set screws removed, since they will add to the diameter of the coupler a little.  Using your magnetized allen wrench, install the first set screw, securing the coupler to the cage part of the bandswitch shaft.  Then push the shaft back into the coupler and install the other setscrew.  Check to be sure the knob is pointing at the right band. 

With both the setscrews tight on the flat part of the shafts, rotate it until you see the other set screw holes and install those setscrews.  That should do it.


This is a view of the 820 bandswitch from underneath. You can see this one is broken. There is also a little access to it from the side of the cage.


The 820 is more difficult, mainly because the hole in the cage where the shaft goes through is just big enough for the shaft and the front panel has to be removed.  The input shaft requires more dis-assembly also.

There is an access hole underneath the chassis.  You will have to go in through there.  Loosen the coupler in the same manner as the above.  To pull the shaft forward, the front panel has to be dis-assembled and removed as it is a secondary shaft driven by a chain.  Loosen all the pieces and it should slide forward.

There is usually enough room to get the new coupler on the shaft, through the bottom access hole, and from the side to help guide it on.  I like to tie a string around the middle of the coupler, so that if it is dropped it can be easily retrieved.  Cut the string when it’s all done. If you start with one (or all) the setscrews in the coupler, then you can use the screwdriver handled allen wrench to hold and position the coupler to slide it on.

This is really a tough one, so give yourself a big pat on the back when you’re done.  Frequent breaks help if the language gets a little coarse.  hihi

Incidentally, don’t worry about the coupler not being plastic.  The shafts on both sides of the coupler are grounded to the chassis.

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