Below You can see my approach to replace failed COPAL encoder used as main VFO in IC756PRO and few next of Icom 756 family.
Few days a go Kris SQ6ODB asked for help with repair his RIG, with jumping frequency, tuning only up or self changing frequency. Apparently it was a sign that encoder is failed, probably because of age, or just previous owner broke it, with improper knob handling.
As You can see, somebody tried to (?) restore proper functioning, by applying some grease or other stuff to release the axle inside. But the main problem wasn't there. The bushing with the axle was just worn out, lead the axle to be eccentric and thus giving bad impulses.
Because original used in 756PRO - COPAL RMS-20-250-201-1P encoder is almost impossible to find, I had to go other way, and find something that can replace it. Sure, we have a few on e-bay, but no one was brand new, and there's no reason to spend $130 for the same piece of not working crap.
Happily found something similar in our electrionic shop, but another problem appear. Original axle is very "long", as You can see above, and those RMS20-250-201-1 found here looks different.
So only solution was to make small rigid clutch and add another piece of axle, to get close to original lenght.
So, here we are - first I had to make original hole in the front cover a little bigger (~13mm max) , to accomodate prepared clutch.
Be very gentle, down below the plastic, we have CFFL PCB - easy to destroy when not handle with care. Now the clutch will fit the hole with some margin.
Thanks to Peter SP2DMB for help with this clutch job. His very old, but still good lathe handled small piece of brass easy and gently. Later, two holes were drilled with M3 thread, and two small sinking screws to get the stuff solid and rigid.
Now it's time to dig in the junk box for old potentiometer - something that will fit into the clutch hole and add some lenght. And voila!
Some final height measurements with caliper, and time to reassembly the rig and test it..
Front cover in place, looking good.
Now the sliding brake in place
And finally rest of the axle added.
Lower part, and upper added piece was carefully set to be as coaxial as possible, and secured with small drop of fast epoxy resin.
Now the RIG operates as good as before for less than $30